Welcome to
HMR’s Central
Laboratory
Clinical laboratory services
in London, UK
Contract laboratory at
Hammersmith Medicines Research
Welcome to
HMR’s Central
Laboratory
Clinical laboratory services
in London, UK
Contract laboratory at
Hammersmith Medicines Research
Tests at central laboratory M – S
If the test you required does not appear on our list, we can set-up and validate the method at your request.
Alternative test name
Mg
Purpose and scope
Magnesium is found mainly in the skeleton; also, the intracellular concentration is much higher than the extracellular concentration. In clinical practice, low blood concentrations of magnesium may be due to diarrhoea, acute pancreatitis, hypoparathyroidism, or drugs, eg diuretics and aminoglycosides. High blood concentrations of magnesium may be due to renal failure. In clinical trials of new medicines, magnesium may be measured to confirm normal blood levels in studies where an abnormal magnesium may adversely affect a study outcome, eg QTc prolongation. Magnesium may also be measured if the trial medicine is expected to affect blood levels of magnesium.
Method
Timed endpoint method
Sample requirements
Serum or heparinised plasma. Centrifuge the samples within 2 hours of collection. It is stable for 1 week at room temperature or at 2–8ºC. Samples can be frozen at –20ºC for up to a month. Once thawed, do not refreeze.
Maximum turnaround time
24 h
Alternative test name
Gelatinase B, MMP-9
Purpose and scope
Matrix metalloproteinases (MMPs) are a family of zinc-dependent enzymes that degrade extracellular matrix proteins. The regulation of MMP activity is important in tissue remodelling, inflammation, tumour growth, and metastasis.
MMP-9 (also known as gelatinase B) is secreted as pro-MMP-9, which is then cleaved into the active enzyme. Pro-MMP-9 is secreted by several cells, including monocytes, macrophages, neutrophils, skin and skeletal cells, and various tumour cells. Specifically, MMP-9 is involved in inflammation, tissue remodelling, wound healing, mobilisation of matrix-bound growth factors, and processing of cytokines. Elevated expression of MMP-9 is usually seen, owing to increased collagen deposition, in: invasive and highly tumorigenic cancers, including pancreatic cancer; metastases to lymph nodes from breast cancer; and brain and bone metastases.
In clinical trials, we measure MMP-9 as a serum inflammatory biomarker in response to new medicines. This assay measures both the pro- and active forms of MMP-9.
Method
Enzyme immunosorbent assay
Sample requirements
Serum. Store serum at 2–8°C for up to 24 h, or at –20°C for up to 4 months.
Maximum turnaround time
Batched
Purpose and scope
The earliest clinical evidence of glomerular damage is urinary albumin concentration above the normal level, but below the detectable range of the conventional urine dipstick method.
Microalbuminuria is a clinically important indicator of deteriorating renal function in diabetics, and is used to monitor both type I and type II diabetes. Increased urinary albumin excretion, both independently and in conjunction with hyperinsulinaemia, also identifies non-diabetic subjects at increased risk of coronary artery disease.
In clinical trials of new medicines, urine microalbumin serves as a marker of renal toxicity.
Method
Enzymatic reaction rate
Sample requirements
Urine. Albumin is stable in urine for 1 month at 2–8°C, and for 7 days at 15–25°C.
Maximum turnaround time
24 h
Alternative test name
MPO
Purpose and scope
Myeloperoxidase (MPO) is an iron-containing protein which was first isolated in 1941. It plays an important role in host defence systems. MPO is an enzyme, present in the aurophilic granules of human neutrophils, and in the lysosomes of monocytes. MPO catalyzes the oxidation of substances through hydrogen peroxide (H2O2), forming hypochlorous acid. The MPO H2O2 system has a toxic effect on many micro-organisms. Hypochlorous acid is 50 times more potent than H2O2 in killing microbes.
This test is used as a marker for: inflammatory activity in the gastrointestinal tract; renal transplant rejection; oxidative stress; and for the differentiation between allergic and infectious asthma.
In clinical trials of new medicines, we measure MPO as an inflammatory biomarker.
Method
Enzyme linked immunoassay (EIA, ELISA)
Sample requirements
Serum
Maximum turnaround time
Batched
Purpose and scope
Myoglobin is a haem protein found mainly in striated muscle cells of both skeletal and heart muscle. A haem protein is a molecule in which a haem group is associated with a protein. Myoglobin has one haem group associated with it, and binds oxygen in a reversible manner. It functions as an oxygen storage unit, supplying oxygen to the working muscles. High concentrations of myoglobin in muscle cells allow organisms to hold their breath for longer. During periods of oxygen deprivation, oxymyoglobin releases its bound oxygen, which is then used for metabolic purposes.
An increase in serum myoglobin concentration occurs after trauma to either heart or skeletal muscle, for example in crush injury, or acute myocardial infarction (AMI). Myoglobin appears in the peripheral blood 2–3 h after the onset of cardiac pain, and reaches a peak after 6-9 h.
Myoglobin is a sensitive indicator of AMI, but is not specific for cardiac muscle, as seemingly minor injury to skeletal muscle may increase the concentration of serum myoglobin, which may lead to the erroneous diagnosis of AMI. However, myoglobin is a very good negative marker, as any suspicion of AMI can be rejected after 2 consecutive negative myoglobin tests.
Owing to rapid elimination by the kidney, the steep increase in serum myoglobin is followed by a rapid fall, so that, in an uncomplicated case, concentrations are often within the normal range by 24 h after the infarct.
In clinical trials of new medicines, myoglobin serves as a marker of cardiac and skeletal muscle damage.
Method
2-site immunoenzymatic assay
Sample requirements
Lithium heparin plasma is the recommended sample. Serum and plasma (heparin or EDTA) are acceptable samples. Samples are stable for 8 h at room temperature, and for 24 h at 2–8°C. For longer periods, store at –20°C.
Turnaround
24 h
Alternative test name
β-NAG, NAG
Purpose and scope
The concentration of N-acetyl-β-D-glucosaminidase (β-NAG) in urine is a sensitive and reliable early indicator of renal disease and tubular damage. In clinical trials of new medicines, urine β-NAG serves as a marker of renal injury.
Method
Enzymatic reaction rate
Sample requirements
Urine. Assay sample as soon as possible, alternatively store sample overnight at 4°C or freeze the sample immediately after collection and store at –20°C.
Maximum turnaround time
24 h
Purpose and scope
Neopterin belongs to the chemical group known as pterins. Neopterin biosynthesis is closely associated with activation of the cellular immune system. Macrophages produce neopterin when stimulated by interferon gamma.
Neopterin serves as a marker of activation of cell-mediated immunity. The cellular immune response is involved or affected by the disease process in conditions such as infections, autoimmune disorders, transplant rejection and malignancy.
In clinical trials of new medicines, neopterin serves as a measure of pharmacodynamic effects on cellular immune system.
Method
Enzyme linked immunoassay (EIA, ELISA)
Sample requirements
Serum. Store serum at 2–8°C for up to 72 h, or at –20°C for up to 6 months.
Maximum turnaround time
Batched
Purpose and scope
The CD11b antigen is part of the CD11b/CD18 heterodimer (Mac-1), which is also known as the C3 complement receptor. CD11b is stored in cytoplasmic granules, and is rapidly up-regulated on the surface of leucocytes after stimulation with chemoattractants that bind to CXCR 2 receptors.
In clinical trials of new medicines, CD11b expression, and CXCR 2 functional receptor occupancy, are used as pharmacodynamic measures of neutrophil activation.
The neutrophil shape change assay is done on whole blood, after red cell lysis. No antibodies are used for staining: the neutrophil population is identified using a light scatter dot plot (forward scatter vs side scatter), and a histogram of the granulocyte population.
Method
Flow cytometry using antibodies to cell-specific markers and forward
Sample requirements
Collect samples into Nunc polypropylene tubes containing 100 μL 0.25 M EDTA (0.5 M EDTA diluted 1:1 with Dulbecco’s phosphate-buffered saline (PBS) without calcium and magnesium).
Pre-warm the Nunc polypropylene tubes containing 100 μL 0.25 M EDTA in a 37°C waterbath for 15min.
Draw up 3 mL venous blood slowly and gently into a syringe, and transfer to the tube without delay.
Immediately put the tube into a water bath at 37°C.
Transport blood from the ward to the laboratory at 37°C.
Maximum turnaround time
Batched
Alternative test name
E2
Purpose and scope
The pituitary gonadotrophins, luteinising hormone (LH) and follicle-stimulating hormone (FSH), control the function and secretion of oestrogens (oestradiol being the most important ovarian oestrogen), progesterone, and testosterone. In addition, LH and FSH regulate the development of ovarian follicles in females, and FSH stimulates spermatogenesis in males. LH and FSH secretion is in turn regulated by the hypothalamic gonadotrophin releasing hormone (GnRH). In the adult female, higher brain centres impose a 28 day menstrual cycle on the activity of GnRH.
In the pre-menopausal woman, the menstrual cycle follows 3 phases: follicular, ovulation and luteal. During the follicular phase, a group of ovarian follicles begin to develop stimulated by FSH, which initially rises and then falls; LH remains low. Under the influence of LH and FSH, oestrogen levels steadily rise; progesterone remains low. Initially there is negative feedback on the pituitary by oestrogen inhibiting LH and FSH secretion. Later there is increased GnRH secretion and increased LH sensitivity to GnRH (positive feedback) which leads to the mid cycle surge of LH which induces ovulation of the lead follicle. During the luteal phase, the follicle differentiates into a corpus luteum which secretes both progesterone and oestradiol. Those hormones then stimulate endometrial proliferation in preparation for implantation. If implantation does not occur, the corpus luteum regresses and the hormones decrease. If implantation and pregnancy do occur, the corpus luteum produces human chorionic gonadotrophin (HCG) which maintains the production of oestrogen and progesterone by the corpus luteum, until the placenta can make sufficient oestrogen and progesterone.
After the menopause, oestrogen levels decline, and, owing to the loss of the negative feedback, LH and FSH levels increase.
Oestrogens are important in maintaining a normal menstrual cycle, and for the development of the female secondary sexual characteristics. The interpretation of oestradiol in women must make allowance for the phase of the menstrual cycle, and whether the woman is pre- or post-menopausal. Oestradiol is raised during ovulation and the early part of the luteal phase, during pregnancy, and declines post-menopausally. In the latter situation, LH and FSH are raised. Oestradiol is mainly bound to sex hormone-binding globulin (SHBG).
Method
Competitive binding immunoenzymatic assay
Sample requirements
Serum or heparinised plasma, samples are stable for 8 h at room temperature and 48 h at 2–8°C or at –20°C for longer storage.
Maximum turnaround time
24 h
Alternative test name
PTH
Purpose and scope
Parathyroid hormone (PTH) is a single-chain polypeptide of 84 amino acids secreted by the parathyroid glands. PTH helps to maintain optimal calcium ion concentrations in plasma. PTH raises circulating ionised calcium concentrations by acting directly on bone and the kidneys. PTH increases the rate of calcium ion flow from bone to the extracellular fluid, and increases both the renal tubular reabsorption of ionised calcium and the renal excretion of phosphate. Long-term regulation of total body calcium by PTH occurs through its stimulation of vitamin D metabolism, which results in enhanced intestinal absorption of calcium.
In healthy individuals, PTH is secreted in response to circulating calcium ion concentrations. Low concentrations of calcium trigger large increases in PTH secretion. Higher concentrations of calcium ions assert negative feedback on the parathyroids, and suppress PTH secretion.
In hypercalcaemia due to primary hyperparathyroidism or to ectopic PTH production, most patients have high PTH concentrations. In contrast, in hypocalcaemia due to malignancy or other causes, PTH concentrations are typically low or normal. PTH concentrations are also high in secondary hyperparathyroidism, which is usually associated with renal failure, as a result of constant stimulation of the parathyroid gland by low calcium concentrations.
Recently-developed assays for intact PTH are sensitive enough to measure circulating concentrations of intact PTH in normal, healthy individuals, and to discriminate between normality and primary hyperparathyroidism.
We measure intact PTH in our trials if there is any reason to suppose that an IMP could affect parathyroid function and calcium metabolism.
Method
Two-site immunoenzymatic sandwich assay
Sample requirements
Serum or plasma (heparin or EDTA). Samples are stable for 4 h at room temperature, 8 h at 2–8°C, or for 6 months at –20°C
Maximum turnaround time
24 h
Alternative test name
PGI
Purpose and scope
Assay of pepsinogen I is used in clinical practice to identify patients who have atrophic gastritis in the fundus and body of the stomach, so are at risk of gastric cancer. PGI is a precursor enzyme of pepsin; it is synthesized by the chief cells and neck cells of the fundus and body of the stomach. Most PGI is secreted into the gastric lumen, but some can be detected in the blood. The serum PGI concentration correlates with the number of chief cells in the gastric mucosa. The loss of chief cells results in a linear decrease of serum PGI. In clinical trials of new medicines, PGI serves as an indicator of medicine-induced damage to the gastric mucosa.
Method
Sandwich enzyme immunoassay technique
Sample requirements
10 h fasting serum, EDTA plasma or heparin plasma sample. If necessary, store serum or plasma refrigerated at 2–8°C for 24 h. For longer storage, freeze samples, preferably at –70°C, but at least at –20°C.
Maximum turnaround time
Batched
Alternative test name
PGII
Purpose and scope
Assay of pepsinogen II is used in clinical practice to identify patients who have atrophic gastritis in the fundus and body of the stomach, so are at risk of gastric cancer. PGII is produced by the chief cells and mucous neck cells of the gastric antrum, and by Brunner’s glands in the proximal duodenum. Pepsinogen I is synthesised by the chief cells and neck cells of the fundus and body of the stomach. Both PGI and PGII are precursors of the enzyme pepsin.
The PGI/PGII ratio decreases linearly with increasing severity of atrophic gastritis in the fundus and body of stomach. The test is used as an additional tool in diagnosis of atrophic gastritis, which is a risk state for gastric cancer. In clinical trials of new medicines, PGII serves as an indicator of medicine-induced damage to the gastric mucosa.
Method
Sandwich enzyme immunoassay technique
Sample requirements
10 h fasting serum, EDTA plasma or heparin plasma sample. If necessary, store serum or plasma refrigerated at 2–8°C for 24 h. For longer storage, freeze samples, preferably at –70°C, but at least at –20°C.
Maximum turnaround time
Batched
Alternative test name
PBMC
Purpose and scope
Peripheral blood mononuclear cells are part of the circulating white blood cell population. PBMCs comprise monocytes and lymphocytes, and can be measured using various methods, including flow cytometry and immunoassays.
Method
Various methods, including flow cytometry and immunoassay
Sample requirements
Cell preparation tube (CPT) containing sodium heparin, Ficoll Hypaque density fluid, and a polyester gel barrier.
Maximum turnaround time
24 h
Alternative test name
PhosB
Purpose and scope
A phospholipid is a lipid that contains a phosphate moiety. Phospholipids are derived from phosphatidic acid, a molecule with glycerol esterified to 2 fatty acids and 1 molecule of phosphoric acid. Phospholipids have a very important role in the structure of the cell membrane, and in the lung as pulmonary surfactants. Phospholipid B is a fraction of plasma phospholipid that can be measured using an enzymatic method. Phospholipid B comprises 3 types of phospholipid: lecithin (phosphatidylcholine), lysolecithin and sphingomyelin.
Method
Enzymatic reaction rate
Sample requirements
Plasma or serum, use only the following anticoagulants: EDTA, heparin, citrate, oxalate or sodium fluoride. Samples are stable at 2–8°C for 30 days.
Maximum turnaround time
24 h
Alternative test name
Inorganic phosphate, Phosphate, PO4
Purpose and scope
Inorganic phosphorus is the most important anion associated with calcium; it is involved in the tubular secretion of hydrogen ions. Measurements of phosphorus (inorganic) are used in the diagnosis and treatment of various disorders, including parathyroid gland, kidney diseases and vitamin D imbalance. Low phosphorus concentration may be caused by hyperparathyroidism and renal disease, which lead to excessive phosphate reabsorption. High inorganic phosphorus concentration may be caused by hypoparathyroidism, and by renal glomerular failure. In clinical trials of new medicines, inorganic phosphate is usually used as a screening test for underlying disease.
Method
Timed endpoint method
Sample requirements
Serum or heparinised or EDTA plasma. Centrifuge the samples within 2 hours of collection. If assay is not completed within 8 hours, serum or plasma can be stored at 2–8ºC for 48 hours or frozen at –20°C for longer storage. Once thawed, do not refreeze.
Collect urine specimens in acid-washed, detergent-free containers. After collection, acidify the specimens to pH <3 with HCl. Perform the assay within 2 hours of collection. For timed specimens, keep the collection container in the refrigerator or on ice during the time period.
Maximum turnaround time
24 h
Purpose and scope
The glycoprotein plasmin inhibitor, previously known as alpha 2-antiplasmin, is a serine protease inhibitor synthesized in the liver. Plasmin inhibitor occurs in the blood in 2 principal molecular forms – plasminogen-binding (PB) and non-plasminogen-binding (NPB). The PB form is a very fast-acting plasmin inhibitor, and is responsible for the rapid plasmin inactivation observed in plasma. NPB reacts 50–100 times more slowly than does PB. The assay measures functional activity of the enzyme. In a clinical laboratory, the test is usually done in patients with coagulation-type bleeding, in whom other factor deficiencies have been excluded. Activity is decreased in liver disease and in disseminated intravascular coagulation (DIC), and may be increased during postoperative bleeding. In clinical trials of new medicines, plasmin inhibitor serves as a marker of effects on blood coagulation.
Method
Chromogenic
Sample requirements
109 mmol/L buffered sodium citrate plasma with a 9:1 ratio of blood to citrate. Store at –40°C for up to 2 months.
Maximum turnaround time
24 h
Purpose and scope
The CD62 antigen, a member of the selectin family of adhesion molecules, mediates the adhesion of activated platelets to neutrophils and monocytes during haemostasis. Upon platelet activation and granule secretion, the α-granule membrane fuses with the external plasma membrane; the CD62 antigen is then expressed on the surface of the activated platelet. PAC-1 recognises an epitope on the glycoprotein gp IIb/IIIa complex of activated platelets at or near the platelet fibrinogen receptor. Platelet activation induces a calcium-dependent conformational change in gp IIb/IIIa that exposes a ligand binding site. PAC-1 binds only to activated platelets, and appears to be specific for that recognition site within gp IIb/IIIa.
Thiazole orange is a nucleic-acid-specific dye. When it binds to RNA or DNA, fluorescence emission increases. That property has been utilised to measure the number of newly-released platelets, using flow cytometry. The newly-formed platelets, called reticulated platelets, differ from more mature platelets in that they contain residual RNA. The percentage of reticulated platelets reflects platelet turnover.
Method
Cytofluorometric method
Sample requirements
109 mmol/L buffered sodium citrate plasma with a 9:1 ratio of blood to citrate. Do not test clotted samples, as the clot traps platelets.
As a precautionary measure, fix part of each blood sample as soon as you receive it: add 0.5 mL Formaldehyde fix solution to 0.5 mL citrated blood.
Maximum turnaround time
24 h
Alternative test name
PFA
Purpose and scope
Platelets are small fragments of cytoplasm derived from megakaryocytes – large cells produced by the bone marrow. Platelets play a crucial part in the blood clotting process, by forming a platelet plug (aggregation). This is a 2-step process. First, platelets bind to the site of the wound (adhesion). Next, the platelets bind to other platelets (activation). Activation can be stimulated by components that are released when the blood vessel is damaged, and by thrombin, which is released during the blood clotting process. When platelets become activated, they release agents that recruit and activate surrounding platelets, and promote the formation of fibrin, which in turn stabilises the platelet plug, stops bleeding, and allows injuries to heal.
Platelet dysfunction may be acquired, inherited or induced by platelet-inhibiting agents. The most common causes of platelet dysfunction are related to uraemia, von Willebrand disease (vWD), and exposure to such agents as acetyl salicylic acid (ASA), eg in aspirin.
In clinical trials of new medicines, measurement of platelet function may serve as a pharmacodynamic test of drug action on platelets.
Method
Artificial activation of platelets to form a thrombus
Sample requirements
Whole blood collected in a tube containing buffered sodium citrate. After collection, gently invert the tube 3–4 times; store the sample, undisturbed, at room temperature for up to 4 h.
Maximum turnaround time
24 h
Alternative test name
K
Purpose and scope
Most of the body’s potassium is intracellular. Serum potassium levels are controlled by renal excretion and aldosterone, extra-renal losses (eg diarrhoea) and uptake of K+ into cells. Cell uptake of K+ is stimulated by insulin, beta-adrenoreceptor agonists and other drugs (eg theophyllines), and decreased by acidosis, cell death, and alpha-adrenoreceptor agonists. Both hypokalaemia and hyperkalaemia may cause muscle weakness and, if severe, may lead to ECG changes, cardiac excitability and fatal arrhythmia.
In clinical practice, low potassium levels are most commonly caused by: diuretic treatment; hyperaldosteronism; renal and nephrotoxic; gastrointestinal losses, beta-agonists and insulin treatment. In clinical practice, high potassium levels are most commonly caused by renal failure secondary to, acidosis or tissue destruction.
In early clinical trials of new medicines, potassium is measured to screen for renal, hepatic or cardiac disease, and to monitor adrenoreceptor activity or nephrotoxicity.
Method
Indirect potentiometry
Sample requirements
Serum or heparinised plasma. Centrifuge the samples within 2 hours of collection. If assay is not completed within 8 hours, store the sample at 2–8°C for 2 days. Samples can be frozen at –20°C for longer storage. Once thawed, do not refreeze.
Maximum turnaround time
24 h
Purpose and scope
Progesterone is a steroid hormone. It is synthesized from cholesterol via pregnenolone, which is then rapidly metabolized to pregnanediol in the liver.
Progesterone plays an important role in the preparation for and maintenance of pregnancy. It is produced mainly in the ovary and the placenta, but a small amount is synthesised by the adrenal cortex in both men and women.
Circulating progesterone concentrations, which are low during the follicular phase of the menstrual cycle, increase sharply during the luteal phase, reaching a maximum at 5–10 days after the mid-cycle luteinising hormone (LH) peak. Unless pregnancy occurs, a steep decline in progesterone concentrations sets in about 4 days before the next menstrual period. This pattern constitutes the rationale behind the well established use of serum progesterone measurements as a simple and reliable method for detecting ovulation.
Measurement of serum progesterone has also been used to check the effectiveness of ovulation induction, to monitor progesterone replacement therapy, and to detect and evaluate patients at risk of abortion during the early weeks of pregnancy.
The interpretation of progesterone concentrations in women must take into consideration whether the woman is pre- or post-menopausal, and the phase of the menstrual cycle. Progesterone is high during the early part of the luteal phase and during pregnancy, and declines after the menopause.
In clinical trials of new medicines, progesterone is not measured routinely. Progesterone may be measured when the investigational medicinal product (IMP) might affect blood concentrations of progesterone.
Method
Competitive chemiluminescent immunometric assay
Sample requirements
Serum samples are stable 7 days at 2–8°C, or 3 months at –20°C. Store samples at –70°C for longer storage.
Maximum turnaround time
24 h
Purpose and scope
Prolactin is a hormone released from the anterior pituitary, and its secretion is under hypothalamic tonic dopamine inhibition. Prolactin stimulates milk secretion in lactating women, but also reduces gonadal activity and GnRH pulsatility. Causes of a raised prolactin include stress, pregnancy, sleep and prolactinoma. Drugs are also a cause, and in particular those with dopamine antagonist activity which reduce the inhibition of dopamine release, and thereby increase the levels of prolactin.
In clinical trials of new medicines, prolactin may be measured to confirm normal blood levels in studies where the medicine is expected to affect levels of prolactin, eg dopamine antagonist activity. In some studies, prolactin might be an intended pharmacodynamic marker.
Method
Simultaneous one-step immunoenzymatic ‘sandwich’ assay
Sample requirements
Serum or heparin plasma. Samples are stable for 8 h at room temperature, 48 h at 2–8°C, or for 6 months at –20°C.
Maximum turnaround time
24 h
Alternative test name
PSA
Purpose and scope
Prostate specific antigen (PSA) is a glycoprotein monomer with protease activity. PSA exists primarily as 3 forms in serum. One form is believed to be enveloped by the protease inhibitor alpha-2 macroglobulin, and lacks immunoreactivity. The second form is complexed to another protease inhibitor, alpha-1 antichymotrypsin (ACT). The third form is present freely, free PSA. The latter 2 forms are immunologically detectable in PSA assays, and are collectively referred to as total PSA. The concentration of free PSA usually ranges from 5 to 50% of the total PSA in serum. This assay is intended to be used with Hybritech (total) PSA to calculate the ratio of free PSA to total PSA expressed as a percentage (percent free PSA).
Measurement of PSA forms is useful in the differentiation of prostate cancer from benign prostatic conditions. In patients with elevated PSA concentrations, men with prostate cancer tend to have lower percent free PSA (free PSA/total PSA) values than men with benign disease.
Percent free PSA may also be used for risk assessment, to determine the probability of cancer for an individual patient. Lower percent free PSA values are associated with higher risk of cancer.
In clinical trials of new medicines, free PSA is not measured routinely, but it may be measured when the study medicine is expected to affect blood concentrations of PSA.
Method
Two-site immunoenzymatic sandwich assay
Sample requirements
Serum, Samples are stable for 3h at room temperature, 24 h at 2–8°C, or for up to 5 months at –20°C.
Maximum turnaround time
24 h
Purpose and scope
Protein C is a plasma protein that inhibits thrombin production, thereby preventing excessive blood clotting. Activated Protein C, with free Protein S as a cofactor, degrades clotting factors Va and VIIIa that are part of the coagulation cascade. Protein C deficiency can be caused by insufficient production by the liver, or by increased use by the body, for example in disseminated intravascular coagulation. In clinical trials of new medicines, Protein C serves as a marker of effects on blood coagulation.
Method
Kinetic
Sample requirements
109 mmol/L buffered sodium citrate plasma with a 9:1 ratio of blood to citrate. Add the sample exactly to the line marked on the tube; under- or overfilled-tubes may give erroneous results.
Centrifuge samples for 15 min at 2000G, and test within 2 h of collection, or as specified by study protocols. For long-term storage, keep samples at –40°C for a maximum of 2 months. Thaw frozen specimens to 37°C for at least 15 min; after thawing, do the assay within 2 h.
Maximum turnaround time
24 h
Alternative test name
PT
Purpose and scope
Prothrombin time (PT) is a measure of the integrity of the blood coagulation system, including factors V, VII, X, prothrombin and fibrinogen, and is used to detect abnormalities in the extrinsic and common pathways. Drugs, and deficiencies and abnormalities of certain coagulation factors, prolong PT. In clinical trials of new medicines, PT serves as a marker of effects on blood coagulation. In some trials, that might be an intended pharmacodynamic effect. The International Normalised Ratio (INR) is the ratio of the PT to a mean normal PT, with correction for the sensitivity of the thromboplastin used. That is calibrated against a primary World Health organisation (WHO) standard thromboplastin.
Method
Absorbance
Sample requirements
109 mmol/L buffered sodium citrate plasma with a 9:1 ratio of blood to citrate. Store at –40°C or lower for up to 2 months.
Maximum turnaround time
24 h
Alternative test name
Retic
Purpose and scope
Reticulocytes are immature red blood cells. They contain remnant RNA material, which distinguishes them from mature red blood cells.
Reticulocytes circulate in the bloodstream for about 2 days, before developing into mature red blood cells. Normally, about 1–2% of red blood cells in the bloodstream are reticulocytes The reticulocyte count increases in anaemia and reflects increased erythroid hyperplasia in the bone marrow. The reticulocyte count is useful in patients with chronic red cell destruction in which the haemoglobin can remain normal, but the reticulocyte count increases. Drugs can cause chronic haemolysis, and in clinical trials of new medicines, the reticulocyte count is a useful marker for haemolysis. The reticulocyte response is reduced when bone marrow function is abnormal, or when there is a lack of erythropoietin stimulus.
Method
Impedance, manual count
Sample requirements
EDTA whole blood
Maximum turnaround time
24 h
Alternative test name
RBP4
Purpose and scope
Retinol-binding protein (RBP) is a small (21 kD) transport protein for vitamin A. RBP forms a complex with prealbumin in blood, but loses its affinity for prealbumin once the vitamin has been delivered to the target cells. The free RBP molecule is filtered rapidly at the glomerulus, and catabolised in the renal tubules after resorption by the proximal tubular cells. In kidney disease with prevailing tubular changes, RBP is not reabsorbed, and so appears in the urine.
In clinical pharmacology studies, we use urinary excretion of RBP 4 as a marker of drug-induced injury to the renal tubule.
Method
Enzyme-linked, immunosorbent assay
Sample requirements
Urine. Adjust the urine to pH between 6 and 8 with 1 N NaOH. Samples are stable at 2-8°C for 2 weeks. For longer storage, freeze at or below –20°C.
Maximum turnaround time
Batched
Alternative test name
SHBG
Purpose and scope
Sex hormone-binding globulin (SHBG) is a glycoprotein synthesized in the liver and responsible for the blood transport of testosterone and oestradiol. SHBG production is regulated by the androgen/estrogen balance, thyroid hormones, insulin and dietary factors. The concentration of SHBG is increased by estrogens and decreased by androgens. Therefore, SHBG production is stimulated by oestradiol and suppressed by testosterone. As a result, SHBG concentrations are higher in women than men. For the same reason, SHBG concentrations in pregnant women are markedly higher.
SHBG is often measured as a supplement to measurement of total testosterone. The ratio of total testosterone to SHBG (the ‘free androgen index’, FAI) is a useful indicator of abnormal androgen concentrations in conditions such as hirsutism syndrome. In clinical trials of new medicines, SHBG serves as a monitoring test of drug effects on testicular or ovarian function.
Method
Two-step immunoenzymatic sandwich assay
Sample requirements
Serum or plasma (heparin). Samples are stable for 8 h at room temperature, 7h at 2–8°C, or for 2 months at –20°C.
Maximum turnaround time
24 h
Alternative test name
Na
Purpose and scope
Disturbances of sodium concentration in the body are caused by disturbances of water balance. That is because sodium content is regulated by volume receptors in the kidney and aorta which adjust the body’s water content to achieve normal osmolality and sodium content.
Hyponatraemia is an electrolyte disturbance that is defined by an elevated sodium level in the blood and the most common abnormality detected in the laboratory. Na+ salt loss in excess of water is due to gastrointestinal, renal loss and loss by osmotic diuresis. Hyponatraemia due to excess water intake may be due to disorders of anti-diuretic hormone function; inappropriate ADH secretion; abnormal ADH; water retention and secondary to drugs (eg oxytocin). Artefactual hyponatraemia may occur when high plasma lipid or protein content reduces plasma volume measured.
Hypernatraemia is usually due to water loss in excess of salt through dehydration, osmotic diuresis, ADH deficiency or insensitivity (pituitary or nephrogenic diabetes insipidus).
In clinical practice, Na+ is a measure of the response to treatment in common conditions such as cardiac failure or hypothyroid disorder. In early clinical trials of new medicines, Na+ aids in screening for above conditions and as a marker of the medicine’s effect on renal function or Na+ homeostasis.
Method
Indirect potentiometry
Sample requirements
Serum, heparinised plasma or urine. For analysis of blood sodium centrifuge the samples within two hours from the time of collection. If assay is not completed within 8 h, store the sample at 2–8°C for 2 days. Samples can be frozen at –20°C for longer storage. Once thawed, do not refreeze.
For analysis of urine sodium, use a 24 h urine collection without additives. If a sample is turbid, centrifuge at 1000G for 10 min. Urine assays should be done within 2 hours of collection. For timed specimens, keep the collection container in the refrigerator or on ice during the time period.
Maximum turnaround time
24 h
Alternative test name
Growth hormone-inhibiting hormone (GHIH), Somatotropin release-inhibiting factor (SRIF)
Purpose and scope
Somatostatin is a 14-amino acid peptide found in the GI tract, and produced particularly by the antral D-cells of the stomach and the upper region of the small intestine. Somatostatin is a powerful inhibitor of various endocrine secretions, including: growth hormone, insulin, VIP, TSH, CCK and gastrin.
Owing to their antagonistic effects, somatostatin analogues can have an important therapeutic value in the treatment of a variety of endocrine tumours.
In patients taking proton pump inhibitors (PPI) and gastrin receptor antagonists, gastric acid secretion is inhibited by blocking the gastrin receptor. Somatostatin assays can therefore be useful in clinical trials to study the effect of drugs, particularly those that affect gastric acid secretion and plasma somatostatin concentrations.
Method
Simplified double antibody-sandwich assay
Sample requirements
Heparin or EDTA plasma samples. Separated plasma can be stored at 2–8°C, and used within 1 week of collection. If unable to assay within this period, store frozen at –20°C for up to 6 months mixed with antimicrobial agent, as that may affect the activity of the conjugate.
Maximum turnaround time
Batched
Alternative test name
SP-D
Purpose and scope
Surfactant protein D (SP-D) is a carbohydrate-binding protein that belongs to the chemical group known as collectin. It is produced by alveolar cells and bronchiolar epithelial cells, and by epithelial cells of various other organs and glands. A form of SP-D is also produced by vascular endothelial cells. From those sources, SP-D may find its way into the blood, where its concentrations may reflect production and penetration at epithelial and endothelial sites.
At epithelia, SP-D takes part in the innate immune defence against invading microorganisms, but does not activate complement. SP-D also interacts with phospholipids and glycolipids, and is a potent inhibitor of peroxidation of phospholipid and low-density lipoprotein (LDL), as well as oxidative cellular injury.
Basal SP-D concentrations are highly variable among individuals, and are largely genetically determined. However, serum SP-D may rise during pulmonary infections and certain non-infectious lung diseases.
In clinical trials of new medicines, we measure SP-D as a serum biomarker of inflammation.
Method
Enzyme linked immunoassay (EIA, ELISA)
Sample requirements
Serum. Store serum at 2–8°C for up to 24 h, or at –20°C to be assayed at a later date.