Urinary catecholamines and metabolites in the immediate postoperative period following major surgery

Background: Induction of anaesthesia can precipitate catecholamine release from an undiscovered pheochromocytoma and induce a hypertensive crisis. However, it is assumed that catecholamine and metabolite values resulting from the effects of surgery per se in the early postoperative period would overlap with the values generated by a tumour, and it is not known how soon after biochemical investigations can be carried out. Aim: To study patterns of urinary catecholamine excretion and the feasibility of biochemical screening for phaeochromocytomas in the immediate postoperative period in otherwise healthy subjects undergoing a single type of major surgical procedure. Methods: Catecholamines and metabolites were measured for each mole of creatinine in single voided urine on one preoperative and four postoperative days in five subjects who underwent elective coronary artery bypass graft surgery with an uncomplicated postoperative course. Reference ranges were established from 33 healthy normotensive volunteers. Results: Excretion of adrenaline, noradrenaline, dopamine, vanillylmandelic acid, and metadrenaline was within normal limits. Normetadrenaline excretion was mildly raised in four patients, but did not exceed 1.5 times the upper reference limit, and returned to normality by the fourth postoperative day. Conclusion: It is feasible to perform simple urinary screening for possible phaeochromocytoma in the immediate postoperative period

Diagnostic scoring for familial hypercholesterolaemia in practice

Purpose of review: Diagnostic scoring for familial hypercholesterolaemia (FH) can be used either to screen for possible FH or guide the selection of patients for genetic (DNA) testing. We review the published diagnostic criteria and discuss the options for future development. Recent findings: Scoring systems have been developed internationally based on lipid values and various combinations of clinical signs and cardiovascular history. The predictive value varies according to the test population, be it lipid clinic referrals, general population, or relatives of patients with FH. Also, there is increasing recognition of genetic heterogeneity in FH so that criteria are of differing predictive value depending on the genetic variant of FH. Summary: These clinical scoring systems are increasingly used to guide selection of patients for FH genetic testing but no single approach has yet emerged as the system of choice. Further refinement of these scoring tools using more sophisticated calculators are superseding the more manual approaches. These are well suited to web-based tools or smartphone applications

The limited value of methylmalonic acid, homocysteine and holotranscobalamin in the diagnosis of early B12 deficiency

Treatment of B12 deficiency is important to prevent progressive neurological and/or hematologic disease but requires a secure diagnosis. The aim of this study was to evaluate second line tests of B12 status as prognostic indicators of a hematologic response to vitamin B12 therapy. Forty-nine patients referred with low, serum vitamin B12 concentrations were treated with intramuscular B12 and re-assessed after 3 months. Methylmalonic acid, homocysteine, holotranscobalamin and neutrophil hypersegmentation index were measured before and after treatment. Before treatment 27/49 patients were anemic or macrocytic of whom 15 had a clear hematologic response. All the tests had a similar prognostic accuracy. Symptomatic improvement did not correlate with hematologic response. Supplementary tests of vitamin B12 status were not significantly better than total serum B12 concentration as predictors of a hematologic response to vitamin B12 therapy

Effect of riboflavin status on the homocysteine-lowering effect of folate in relation to the MTHFR (C677T) genotype

Background: Riboflavin (vitamin B2) is the precursor for FAD, the cofactor for methylenetetrahydrofolate reductase (MTHFR). MTHFR catalyzes the formation of 5-methyltetrahydrofolate, which acts as a methyl donor for homocysteine remethylation. Individuals with the MTHFR 677CT mutation have increased plasma total homocysteine (tHcy) concentrations, particularly in association with low folate status. It has been proposed that riboflavin may act together with folate to lower plasma tHcy, particularly in individuals with the thermolabile MTHFR T variant. Methods: We measured B-vitamin status and plasma tHcy in 126 healthy individuals 20–63 years of age (42 CC, 42 CT, and 42 TT MTHFR genotypes) at baseline and after three interventions (4 months): placebo plus natural diet; daily 400 µg folic acid supplement plus natural diet; and increased dietary folate to 400 µg/day. Results: At baseline and after nutritional intervention, lower riboflavin status was associated with increased plasma tHcy concentrations. Plasma tHcy was 2.6 µmol/L higher in the lowest plasma riboflavin quartile compared with the highest (P <0.02) and was 4.2 µmol/L higher in the highest erythrocyte glutathione reductase activation coefficient (EGRAC) quartile compared with the lowest (P <0.001). This effect was not restricted to those with the T allele. Folic acid given as a 400 µg/day supplement appeared to exacerbate a tendency toward riboflavin deficiency, as suggested by an increase in the proportion of individuals with EGRAC 1.4 from 52% to 65% after supplementation (P <0.05). Conclusions: Folate and riboflavin interact to lower plasma tHcy, possibly by maximizing the catalytic activity of MTHFR. The effect may be unrelated to MTHFR genotype

Web based tools to assess eligibility for genetic testing for Familial Hypercholesterolaemia (FH)

Selection of patients who are appropriate for genetic testing for FH is a balance between diagnostic yield and cost. The Wales FH service has implemented a clinical scoring system to guide the selection of patients based on lipid levels, personal and family history of cardiovascular disease plus physical signs. In an evaluation of 623 patients referred to lipid clinics, the proportion of patients with a mutation ranged from 4% in those scoring 5 or less to 85% in those scoring >15

Relationship between measurements of non-HDL-cholesterol and LDL-cholesterol in Familial Hypercholesterolaemia

Familial Hypercholesterolaemia (FH) is a monogenic disorder of Low Density Lipoprotein (LDL) metabolism which can be specifically diagnosed by genetic testing. However LDL-cholesterol (LDL-C) estimation has the drawback that it requires a fasting sample, because the Friedewald formula uses a factor relating to fasting triglyceride. Also other cholesterol containing lipoproteins are atherogenic and should be considered as part of cardiovascular risk assessment. Recent guidelines from National Institute for Health and Care Excellence (NICE) recommend non-HDL cholesterol (non HDL-C) for assessment of cardiovascular risk

Nutritional advice to increase soluble fibre intake does not change plasma folate or homocysteine in men with angina: a randomised controlled trial

Objective: To study the effect of advice to increase dietary soluble fibre, including fruit and vegetables, on plasma folate and homocysteine in men with angina. Design: Data were collected on a subset of subjects from the Diet and Angina Randomised Trial (DART II). In a randomised (2 × 2) factorial design, subjects received advice on either, neither or both interventions to: (1) increase soluble fibre intake to 8.0 g day−1 (fruit, vegetables and oats); (2) increase oily fish intake to 2 portions week−1. Those who received soluble fibre advice were compared with those who did not. Subjects were genotyped for C677T variant 5,10-methylenetetrahydrofolate reductase (MTHFR). Setting/subjects: Seven hundred and fifty-three male angina patients were recruited from general practice. Results: Plasma homocysteine concentrations were at the upper end of the normal range (median 11.5, 25% 9.4, 75% 14.0 μmol l−1). Baseline intake of fruit and vegetables was positively correlated with plasma folate (rs = 0.29, P < 0.01). Smokers had lower intakes of fruit and vegetables, lower plasma folate and higher homocysteine (all P < 0.01). Homozygotes for variant MTHFR had higher homocysteine concentrations at low plasma folate (P < 0.01). Reported intakes of fruit and vegetables and estimated dietary folate increased in the intervention group (ca. +75 g day−1, P < 0.01 and ca. +20 g day−1, P < 0.05, respectively). However, neither plasma folate (baseline/follow-up 4.5 vs. 4.4 μg l−1, P = 0.40) nor homocysteine (baseline/follow-up 11.7 vs. 11.7 μmol l−1, P = 0.31) changed. Conclusions: Plasma homocysteine, a cardiovascular risk factor, is influenced by MTHFR genotype, plasma folate and smoking status. Dietary advice successfully led to changes in fruit and vegetable intake, but not to changes in plasma folate or homocysteine, possibly because the fruits and vegetables that were chosen were not those richest in folate