Profiles and screens

The radical-scavenging antioxidants in human serum represent a heterogeneous group of substances, some synthesised in the body and some derived exclusively from the diet. Serum proteins, for example, can scavenge free radicals if they have available tyrosine or cysteine groups. Uric acid, which is also present in the serum in substantial concentrations, is another major free radical-scavenger. Circulating albumin and uric acid together provide the major source of antioxidant activity in normal human plasma. Using a synthetic radical cation, generated in the test tube as the basis for a laboratory test, the reference interval for serum total antioxidant activity is 1.32 – 1.58 mmol/L (Trolox equivalents). The reference interval for serum nutritional antioxidants (taken as the total serum activity minus that of the serum albumin and uric acid) is 450 – 800 µmol/L (Trolox equivalents). Oxidative stress, i.e. the presence of a relative excess of pro-oxidants in the extra-cellular fluid, causes a fall in these figures. Studies on diabetic patients, asthmatics, subjects with cardiovascular problems and premature babies, have confirmed the usefulness of these measurement in certain clinical situations and we feel that there are many other patients in which a knowledge of the combined activity of all the circulating antioxidants would assist in clinical assessment and care. Deficiencies of vitamin C (reference interval 34 – 114 µmol/L) or vitamin E (reference interval 25 – 60 µmol/L) usually only have a marginal effect on these figures and hence levels of these vitamins should be assessed individually.

Serum & RBC Cu, ceruloplasmin, vitamin E, RBC GSH-Px, RBC fragility, superoxide dismutase and serum ß-carotene.

[1 x Gold top tube (SST), 1 x green top heparin tubes, samples must reach the laboratory within 24 hours and before 4pm, no supplements on the day of the test]

Fasting serum is collected and a further sample is taken 1 hour after an oral loading dose of 50mg of zinc. An increase in copper is usually found. A reduction in copper response to zinc is seen in copper deficiency and some patients with chronic fatigue syndrome.

The Biolab Health Risk Profile is a group of nutrition-related biochemistry tests that are produced on a non-urgent basis. Interpretative comments, aimed primarily at the requesting physician, are appended to the report.

The profile covers serum vitamins and minerals, red cell membrane fatty acid levels, antioxidant enzymes, liver- and bone-related enzymes, serum proteins and blood HbA1c. We periodically re-arrange and re-select suitable analytes for inclusion in the profile, while trying to keep it as economical as possible.

Under vitamins we analyse A, C and E and also the carotenoids beta-carotene, lycopene and lutein. With regard to vitamin A, we now find many subjects with high levels, reflecting the over-inclusion of retinol in multi- supplements and in mixed fatty acid preparations. Vitamin E and C deficiencies are still an occasional problem, but probably less so now that the public is much better informed about the need to consume a diet rich in these vitamins. The levels of carotenoids in blood reflect the extent of their inclusion in the diet - carrots for carotene, tomatoes for lycopene and fresh vegetables for lutein - as well as the absorption of carotenoids from the gut.

Under minerals we analyse zinc, copper, chromium, selenium and magnesium. Zinc and magnesium deficiencies remain the most common nutritional problems we encounter. Our selenium analytical method has been much improved over the past year and the results, taken together with the glutathione peroxidase isoenzyme activities which we now report, show that selenium deficiency is a less common finding in our patient population than was previously thought.

We also measure red cell fatty acids as a reliable indicator of omega-6 and omega-3 series fatty acid deficiencies, which are very common in our patient population.

Antioxidant enzyme activities are induced by oxidative stress and can be expected to rise in response to conditions that induce oxidative stress. These enzymes have activities that are below normal where there are co-factor deficiencies (e.g. copper for superoxide dismutase, selenium for glutathione peroxidase). Paraoxonase is an antioxidant enzyme, carried on HDL, whose activity helps to explain the some of the unaccounted anti-atherosclerotic activity of HDL. Paraoxonase activity measurements were recently added to Health Risk Profile reports.

Other enzymes measured reflect bone or hepatic function (or both, as is the case for alkaline phosphatase). TRAP is measured as a marker of osteoclastic activity. Prostatic acid phosphatase activity (PAP) is measured as a marker of prostate tissue proliferation - and, given the current feelings about prostate-specific antigen measurement, we are glad we have kept this measurement going over the years. Lactate dehydrogenase is used as a non-specific marker of tissue damage, but usually reflects hepatocellular damage, bile acid measurement and gamma-glutamyl transferase activity reflect hepatic dysfunction - cholestatic dysfunction in the case of bile acids and increased hepatocellular permeability in the case of gamma-GT. Glutathione-S-transferase (GST) activity increases with hepatocellular microsomal enzyme induction, primarily reflecting drug intake, both therapeutic and recreational.

Serum albumin can be used in the general assessment of nutritional status, protein loss, hydration and liver disease. Albumin levels also fall as part of the acute phase response (inflammation). Serum globulin levels reflect immunoglobulin synthesis and hence antibody production and hepatic dysfunction. Serum C-reactive protein levels also reflect inflammation and the acute phase response, but CRP is now also regarded as an independent risk factor for the development of atheroslcerotic disease.

HbA1c (glycosylated haemoglobin) levels, as described earlier, reflect the control of blood glucose over the previous 60 days and hence act as a marker for the risk of developing diabetes mellitus. We have recently updated our method for measuring HbA1c and the values we report are formatted in accordance with the current international recommendations.

Note: The Health Risk Profile should be used in conjunction with routine haematological and biochemical screens.

[1 x Gold top tube (SST), 1 x Blue - trace element free EDTA tube, 1 x Green top heparin tube, 2 x lavender top EDTA tube, preferably 3 hr fast and no nutritional supplements for 24 hours prior to the test]

As above, but now includes vitamin D, vitamins B1, B2, B6, B3 and biotin, and homocysteine.

[As above plus: 1 x Gold top tube (SST), 1 x Green top heparin tube, Special kit for homocysteine]

Total and bone alkaline phosphatase and acid phosphatases are measured to assess the balance between bone formation and bone resorption. Calcium and phosphorus are measured in both urine and blood together with tests to assess the status of a range of nutrients essential to bone metabolism. The profile complements rather than replaces bone mineral density measurement.

[Gold top tube (SST), Green top heparin tube, 24 hour urine collection, no nutritional supplements for 24 hours before testing]