David Stansbie

C677T (thermolabile alanine/valine) polymorphism in methylenetetrahydrofolate reductase (MTHFR): its frequency and impact on plasma homocysteine concentration in different European populations

A common polymorphism has been described in the methylenetetrahydrofolate reductase (MTHFR) gene, substituting an alanine (A) for a valine (V), where the V allele results in a thermolabile enzyme with reduced activity. This polymorphism is easily detectable by PCR amplification and digestion with HinfI restriction enzyme. We describe the use of the MADGE high throughput genotyping system for rapid typing of this polymorphism. Seven hundred and eighty five individuals participating in the European Atherosclerosis Research Study II (EARS II), aged 22-25 from 14 universities in 12 countries across Europe were genotyped for this polymorphism. The frequency of the V allele was 0.32 overall (95% CI; 0.30-0.35), but was significantly lower in the Baltic countries (0.23; 95% CI; 0.19-0.28) compared with the other regions of Europe (0.37; 95% CI; 0.32-0.38) (P < 0.001). Individuals homozygous for the V allele had statistically significant (P < 0.001) higher plasma homocysteine (16.5 micromol/l) compared with those heterozygous for an A allele (10.4 micromol/l) or homozygous for an A allele (10.0 micromol/l). This effect was seen in all countries and regions of Europe. Mean plasma homocysteine levels were significantly higher in the South compared to the Baltic, UK and Middle regions (P = 0.001), but this difference was not explained by the difference in the frequency of the V allele in the samples. This polymorphism explained 12.3% of the total sample variance in plasma homocysteine, other measured factors (smoking, alcohol consumption, systolic blood pressure, physical activity) explained 0.7%. This study demonstrates the large and consistent impact of the thermolabile MTHFR variant on plasma homocysteine levels in different European populations, and shows a regional difference in the levels of homocysteine that must be explained by other genetic or environmental factors.

Assessment of homocysteine as a cardiovascular risk factor in clinical practice

Elevated plasma total homocysteine concentrations are a marker of vitamin deficiency and a risk factor for cardiovascular disease. It is possible that vitamin supplementation with folic acid and other B vitamins, which lower plasma homocysteine concentrations, may reduce the risk of cardiovascular disease. Large-scale clinical trials are currently underway to assess the homocysteine hypothesis of cardiovascular disease. Pending the outcome of such trials, measurement of plasma homocysteine concentrations in people at high risk of cardiovascular disease may help to identify patients who could benefit from more intensive treatment of classical cardiovascular risk factors. The introduction of immunoassays for homocysteine determination has made assessment of homocysteine status accessible to most routine hospital laboratories, and this review summarizes the evidence on why and how to assess homocysteine as a risk factor for cardiovascular disease in clinical practice.

Cost-effective strategy for the serological investigation of coeliac disease

Increased numbers of requests for serological investigation of coeliac disease, and a local trend to request both anti-gliadin antibodies (AGA) and anti-endomysium antibodies (AEA) simultaneously, resulted in cost pressures that prompted a review of our practice. Serology results from all patients (771 children, 511 adults) investigated for coeliac disease over a 3-year period were compared with small intestine histology where available. IgG AGA and IgA AGA were measured by enzyme-linked immunosorbent assay (in-house), IgA AEA by immunofluorescence (send-away contract). Overall diagnostic performance was as follows: AGA sensitivity 84%, specificity 88%, positive predictive value (PPV) 24%, negative predictive value (NPV) 99%; AEA sensitivity 88%, specificity 97%, PPV 65%, NPV 99%. Results showed AGA, with its high NPV, to be a suitable first-line test to exclude coeliac disease. The high specificity of AEA makes it a suitable confirmatory test when AGA is positive. Introduction of this step-wise approach to coeliac disease investigation resulted in cost savings of at least £5000 per year without detriment to the clinical service.

Addition of 3-Deazaadenosine to Vacutainer Tubes Stabilizes Whole-Blood Homocysteine for At Least 6 Hours at Ambient Temperature

Increased plasma homocysteine is now well established as a risk factor for cardiac, cerebral, and peripheral vascular disease (1). Despite this, the test is not widely available. This is partly because of practical difficulties in sample collection. The homocysteine concentration increases in whole blood by up to 10% per hour unless samples are kept on ice and separated within 60 min. The introduction of containers with 3-deazaadenosine (3-dad; DS30 Homocysteine Blood Collection Tubes; Drew Scientific Ltd.), described in a recent report (2) in the Journal, may solve the problem, but they are not in widespread …