[Measurement of methylmalonic acid, homocysteine and methionine in cobalamin and folate deficiencies and homocysteinuria]

BACKGROUND

Deficiencies of cobalamin (vitamin B12) or folate are common conditions that predispose for anemia and chronic diseases. An elevated concentration of methylmalonic acid in plasma/serum is an indicator of cobalamin deficiency, whereas an increased concentration of total homocysteine in plasma occurs with deficiency of both cobalamin and folate. The biomarkers methylmalonic acid and homocysteine are therefore complementary, and the combination is often requested when conventional tests fail to provide an unambiguous diagnosis.

MATERIAL AND METHODS

This article summarizes publications, retrieved through Medline, describing novel strategies for laboratory diagnostics of cobalamin and folate deficiencies.

RESULTS AND INTERPRETATION

Adverse health effects of food fortification and uncritical supplementation with folic acid are explanations for a renewed interest in individual diagnosis of B-vitamin deficiency. Interpretation of methylmalonic acid and homocysteine test results requires knowledge of kidney function, as renal failure causes an increase in the concentrations of both metabolites. Homocystinuria is a condition that also causes increased levels of plasma homocysteine. This condition is an inborn error with a higher prevalence (1 : 6400) than previously recognized; which usually responds favourably to homocysteine-lowering therapy. Patients with homocysteinuria have high levels of methionine in plasma and knowledge of plasma methionine concentration may therefore distinguish these patients from those with conditions like B-vitamin deficiencies or renal failure, which are accompanied by normal or low to normal methionine concentrations. Complementarity, logistics, small sample volumes and costs therefore favour a combined analysis of methylmalonic acid, homocysteine and methionine in a single sample. Such an approach also allows assessment of cobalamin status in small volume capillary blood samples drawn from newborns and infants.

LabCorp v. Metabolite Laboratories: The Supreme Court listens, but declines to speak

In the United States, a longstanding legal rule exists against patenting natural phenomena. The Supreme Court recently had an opportunity to help define the boundaries and clarify the implications of this "natural phenomenon doctrine" in Laboratory Corporation of America v. Metabolite Labs., dismissed as improvidently granted. This article argues that the natural phenomenon doctrine renders both the patent claim at issue in LabCorp, and the patents that directly or indirectly claim biological correlations between genotypes and medical phenotypes, invalid or unenforceable under U.S. patent law.

Epidemiological survey of vitamin deficiencies in older Thai adults: implications for national policy planning

OBJECTIVE

To examine the prevalence and risk factors of vitamin deficiencies among older Thai adults.

METHODS

The cross-sectional study was conducted in four rural communities, one from each of the four main regions of Thailand. In total, 2336 subjects aged 60 years and over were recruited. Anthropometric variables, demographic data, blood glucose and lipid profile, albumin, globulin and blood levels of vitamin A, beta-carotene, folic acid, vitamin B12, vitamin C, vitamin E and vitamin B1 were all measured.

RESULTS

The prevalence of vitamin deficiencies was 0.6% for vitamin B12, 6.1% for vitamin A, 9.9% for vitamin C, 30.1% for vitamin B1, 38.8% for erythrocyte folate, 55.5% for vitamin E and 83.0% for beta-carotene. Male gender was a common risk factor for at least three vitamin deficiencies, i.e. beta-carotene, folate and vitamin E. Being a manual worker was a common risk factor of beta-carotene and vitamin B1 deficiency. Poor income was found as a risk factor only in erythrocyte folate deficiency while increasing age was a significant factor only in vitamin C deficiency.

CONCLUSION

The prevalence of vitamin deficiencies among older Thai people was quite different from that found in Western countries, reflecting different socio-economic backgrounds. Vitamin deficiency was not only from poor food intake but also from the dietary habit of monotonous food consumption in older people. Some common associated factors of atherosclerosis were also significantly related to folate and vitamin E deficiencies.

[Serum homocysteine, folate and vitamin B12 in venezuelan elderly]

The anatomical and physiological changes of aging make elderly people a vulnerable group to malnutrition and specific deficiencies of nutrients such as vitamin B12 and folate. This study was aimed to establish relationships among serum vitamin B12, folate, homocysteine concentrations and dietary intake and adequacy. Fifty five male and female elderly (60 and more years), free-living, were assessed. Measurements were: serum vitamin B12 and folate by radioimmunoanalysis (RIA), homocysteine by polarized fluorescence immunoassay, nutrient intake by three 24 hours recalls and food frequency questionnaire. Nutritional status was determined by Body Mass Index (BMI). Serum vitamin B12 and folate were at normal range (423,3+/-227,6 pmol/l and 6,4 +/- 4,5 mg/ml), but 17,5% of elderly had B12 deficiency and 12% had folate deficiency. Serum homocysteine was higher than reference values (15,8+/-4,4 mmol/l), but 47,5% showed concentrations above 15 mmol/L, male population showed higher mean value (p: 0,01). Nutrient intake was inadequate by deficiency. BMI indicated 11,8% of undernutrition, 29,4% of overweight and 20,6% of obesity A negative and inverse correlation between homocysteine and serum folate was found. Results suggest a biochemical deficiency of B12 and folate that is expressed as elevated homocysteine levels. These finding represent a high cardiovascular risk factor for this elderly group.

Diminished Need for Folate Measurements Among Indigent Populations in the Post Folic Acid Supplementation Era

Context.—The mandated fortification of processed grains with folic acid in the United States and Canada in 1998 was intended to reduce the incidence of neural tube defects in pregnant women. The incidence of folate deficiency in most populations has declined dramatically since then.

Objective.—To determine the rate of folate deficiency in a cohort of indigent patients, a population among those at highest risk for folate deficiency.

Design.—Using data from 3 years (1997, 2000, and 2004), we examined results of laboratory tests for red blood cell folate ordered at 3 hospitals that predominately service the needs of indigent patients. Folate concentration cutoffs were 160 ng/mL (363.6 nmol/L) and 94 ng/mL (213 nmol/L).

Results.—Using a red blood cell folate cutoff concentration of 160 ng/mL (363.6 nmol/L), the combined incidence of folate deficiency decreased from 4.8% in 1997 to 0.6% in 2004. At a cutoff of 94 ng/mL (213 nmol/L), the incidence went from 0.98% to 0.09% in 1997 and 2004, respectively. Even when the folate concentration was found to be low, the majority of these subjects did not have macrocytosis.

Conclusions.—These data suggest that folate deficiency has become a rare event in the United States, and the utility of routine folate measurements for patients with anemia and/or increased mean corpuscular volume are difficult to justify.

Recurrent dystonia in homocystinuria: a metabolic pathogenesis

Dystonia complicating homocystinuria is extremely rare in the absence of thromboembolic disease. We report a unique case of recurrent dystonia in a patient with homocystinuria secondary to pyridoxine-unresponsive cystathionine beta-synthase deficiency. Brain MRI was normal. Two biochemical markers for homocystinuria, homocystine and methionine, were markedly elevated during periods when our patient manifested dystonia. These findings suggest that accumulation of sulfur-containing amino acids may contribute to the pathophysiology of dystonia in patients with homocystinuria.

Glomerular filtration rate as measured by serum cystatin C is an important determinant of plasma homocysteine and serum methylmalonic acid in the elderly

OBJECTIVES

To explore the dependence of glomerular filtration rate (GFR) on plasma total homocysteine (tHcy) and serum methylmalonic acid (MMA), as well as the consequences for the diagnosis of cobalamin and/or folic acid deficiency in an elderly community-dwelling population.

DESIGN AND SETTING

Population-based study of 209 community-dwelling subjects, mean age 76 years.

INTERVENTIONS

Four months' treatment study with oral vitamin B(12), folic acid and B(6) or placebo.

MAIN OUTCOME MEASURES

Determinants of tHcy and MMA: cystatin C as a marker of GFR and serum/plasma concentrations of vitamin B(12) and folate, age and sex.

RESULTS

Elevated cystatin C (>1.55 mg L(-1)) was found in 31.3% (men) and 13.0% (women). Elevated tHcy (> or = 16 micromol L(-1)) occurred in 53% and elevated MMA (> or = 0.34 micromol L(-1)) in 11% of all subjects. When GFR was taken into consideration, the proportion of elevated tHcy was reduced to 10% (20/209), whilst the proportion of elevated MMA was unchanged. Cystatin C was correlated with tHcy (r = 0.45, P < 0.001) and with MMA (r =0.28, P < 0.001), independently of vitamin B(12)- and folate status. According to multiple regression, independent predictors for tHcy were plasma folate (15%), cystatin C (11%) and vitamin B(12) (4%), and for MMA, cystatin C (8%) and vitamin B(12) (2%).

CONCLUSIONS

The prevalence of elevated tHcy may be overestimated in elderly populations unless GFR is taken into account. Nomograms for evaluation of tHcy and MMA in relation to both cystatin C and serum creatinine are presented.

Systematic review: managing anaemia in Crohn's disease

BACKGROUND

Anaemia is a serious complication of Crohn's disease that triggers hospitalization and, if not interfered with, may lead to death.

AIMS

To systematically summarize and compare the literature on anaemia in Crohn's disease.

METHODS

For this systematic review the literature was searched for English-language articles using anaemia, Crohn* and IBD as key words. 144 articles were identified and sorted according to the following topics: prevalence, aetiology, diagnostic tests and therapy.

RESULTS

The reported prevalence of anaemia varied between 6.2% and 73.7%, with higher reported frequencies in older studies and in in-patients. Iron deficiency is the most common underlying condition. Vitamin B12 deficiency is related to the extent of ileal resection but has rarely impact on anaemia. Diagnostic criteria are not established and treatment guidelines are missing. Oral iron supplementation seems effective for short periods but intolerance leads to discontinuation in up to 21%. Eleven of 11 studies show that oral iron enhances intestinal inflammation and colon carcinogenesis in animal models of colitis. Intravenous iron supplementation with iron sucrose has been tested in over 250 Crohn's disease patients, is safe, effective and does not carry such hazards.

CONCLUSIONS

As disease activity is determining the degree of anaemia in Crohn's disease, implementation of more effective therapy for Crohn's disease will lower its incidence. However, further studies regarding the safety and effectiveness of iron supplementation are needed.

Methylmalonic acid and cognitive function in the Medical Research Council Cognitive Function and Ageing Study

BACKGROUND

An elevated blood concentration of homocysteine is an established risk factor for cognitive impairment and dementia, but associations between cognition and methylmalonic acid (MMA), a related metabolic marker of vitamin B-12 deficiency, are less clear.

OBJECTIVE

The aim was to determine the utility of serum MMA and holotranscobalamin as markers of vitamin B-12 status in relation to cognitive function and to investigate their association with discrete cognitive domains.

DESIGN

This was a cross-sectional survey of 84 nondemented elderly participants (aged >69 y) from the Welsh cohort of the Medical Research Council's Cognitive Function and Ageing Study. Cognitive status was determined by Mini-Mental State Examination (MMSE) and the Cognitive Section of the Cambridge Mental Disorders of the Elderly Examination (CAMCOG).

RESULTS

Nearly one-half (43%) of the persons selected had likely metabolically significant vitamin B-12 deficiency. Higher MMA concentrations were associated with lower MMSE scores independent of age and education (P = 0.007). MMA concentration correlated inversely with CAMCOG scores of ideational praxis (P < 0.05) and language comprehension (P < 0.05) and expression (P < 0.01). Serum folate correlated weakly but significantly with language (P < 0.05), remote memory (P < 0.05), and constructional and ideational praxis scores (P < 0.05 and P < 0.01, respectively).

CONCLUSION

The high prevalence of likely metabolically significant vitamin B-12 deficiency in the elderly is associated with lower cognitive function scores and particularly with lower scores of language comprehension and expression.

Nutritional megaloblastic anemia in young Turkish children is associated with vitamin B-12 deficiency and psychomotor retardation

We aimed to investigate the presence of psychomotor retardation, physical and laboratory examination in infants with megaloblastic anemia. Inclusion criteria for the study were; age 9 to 36 months, refusal of food except for breast and cow milk, loss of appetite, developmental delay, significant pallor, and hypersegmentation neutrophils in the peripheral blood smear. A total of 33 children fulfilling the inclusion criteria were enrolled among 3368 patients attending Pediatric Outpatient Clinics of şirnak-Cizre State Hospital between January 25, 2004 and May 5, 2004. Mean age was 16.4 months. Thirty-two patients had Vitamin B12 deficiency, 1 patient had folate deficiency, and 10 patients had combined vitamin B12 and folate deficiency. Statistically, a positive significant relationship was detected between serum vitamin B12 levels and mean corpuscular volume (P = 0.001, r = 0.56), and between vitamin B12 levels and hemoglobin (P = 0.004, r = 0.49). We believe that preventative measures such as fortification of flour with vitamin B12, nutritional support with vitamin B12 for the mother during pregnancy and nursing, provision of adequate primary preventive health services, and starting complementary food after 6 months of age are important determinants for preventing megaloblastic anemia.

Four-way calibration applied to the simultaneous determination of folic acid and methotrexate in urine samples

First-, second- and third-order calibration methods were investigated for the simultaneous determination of folic acid and methotrexate. The interest in the determination of these compounds is related to the fact that methotrexate inhibits the body's absorption of folic acid and prolonged treatment with methotrexate may lead to folic acid deficiency, and to the use of folic acid to cope with toxic side effects of methotrexate. Both analytes were converted into highly fluorescent compounds by oxidation with potassium permanganate, and the kinetics of the reaction was continuously monitored by recording the kinetics curves of fluorescence emission, the evolution with time of the emission spectra and the excitation-emission matrices (EEMs) of the samples at different reaction times. Direct determination of mixtures of both drugs in urine was accomplished on the basis of the evolution of the kinetics of EEMs by fluorescence measurements and four-way parallel-factor analysis (PARAFAC) or multiway partial least squares (N-PLS) chemometric calibration. The core consistency diagnostic (CORCONDIA) was employed to determine the correct number of factors in PARAFAC and the procedure converged to a choice of three factors, attributed to folic acid, methotrexate and to the sum of fluorescent species present in the urine.

Factors associated with risk of low folate intake among adolescents

OBJECTIVE

To evaluate factors associated with the risk of low folate intake among adolescents.

METHODS

We employed cluster sampling, using a random selection of 40 representative census sectors and households within those sectors, including all individuals between 10 and 19 years of age. The weight, height and skin folds of subjects were measured and socioeconomic data on their families were collected. A 24-hour dietary recall and frequency questionnaire were used to estimate the quantity and frequency of folate intake. Folate consumption was quantified using Nutwin software. Risk of low folate intake was defined as Folate consumption below the estimated average requirement. The statistical analysis employed hierarchical logistic regression.

RESULTS

A total of 722 adolescents were investigated and their mean folate intake was 145+/-117 microg. The frequency of subjects at risk of having a lower than recommended folate intake was 89%. Adolescents had a greater risk of inadequate folate intake if their body mass index was at or above the 85th percentile, their waist circumference was at or above the 80th percentile or they had a family history of cardiovascular disease. Adolescents who ate beans and dark green vegetables less than four times a week also exhibited an increased chance of having folate intake below recommended levels.

CONCLUSIONS

These adolescents present a high risk of low folate intake and this risk is linked with increasing age, waist circumference above the 80th percentile and low frequency of beans and dark green vegetables consumption.

A laboratory algorithm with homocysteine as the primary parameter reduces the cost of investigation of folate and cobalamin deficiency

Analyses of total homocysteine (tHcy) and to some extent methyl malonic acid (MMA) have become increasingly used in Sweden, primarily for investigating folate and cobalamin deficiency. This has led to increasing costs for diagnosis and laboratory testing, since clinicians still order the established tests, cobalamin and folate. The purpose of this study was to compare the profile of test parameters in six Swedish counties, using laboratory statistics from 2003, and to relate these to medical prescriptions for folate and cobalamin in the same counties. We also wanted to evaluate whether or not a laboratory algorithm with tHcy as the primary test-parameter, followed by vitamin analyses only when tHcy is above a certain decision limit, could reduce the expanding cost of diagnosing folate and cobalamin deficiency. For this analysis we used patient results from two counties in Sweden collected during 2003. There is a slight positive correlation between resources spent upon tests and resources spent upon treating these deficiencies, and a laboratory algorithm based upon initial analysis of tHcy, instead of conventional clinical requests for all parameters, could save approximately 30% of laboratory costs. A typical annual saving in one of these counties (ca. 260,000 inhabitants) by implementing this algorithm would be ca 100,000.

Role of folate deficiency on erythropoietin resistance in pediatric and adolescent patients on chronic dialysis

Unlike iron therapy, folate use is not a standard of care in hemodialysis (HD) patients. Despite iron repletion, poor response to erythropoietin (EPO) treatment is common. Theoretical evidence for folate deficiency (FD) includes chronic blood loss, inflammation, malnutrition, and nutrient loss during dialysis. Due to poor diagnostic standards, early studies failed to establish a role for FD in EPO resistance. Given that hematological response to therapeutic intervention is the gold standard for FD, its diagnosis was therefore based on composite scoring of RBC and/or folate indices. Fifteen subjects (8-20 years) on chronic HD were enrolled in this study. No folate supplement was given in the first six months. Thereafter, 5-mg folic acid was administered orally after HD sessions over a six-month period. Folate indices before and after treatment were compared using percentage differences and paired t-tests. After folate use, the mean Hb increased by 11.4%, while MCV and RDW were reduced. Similarly, 4 of the 15 subjects each had a > or = 20% rise in Hb and a > or = 5% reduction in MCV, while 46.7% had a > or = 2.5% reduction in RDW. Mean RBC folate increased by 24%, while FD scores reduced from 3.8+/-1.2 to 0.4+/-0.7, and the EPO requirement by 90%. In contrast to previous studies, 26.7% of study subjects met the criteria for FD. Furthermore, the substantial (post-folate) reduction in the EPO requirement validates the need for therapeutic intervention, and therefore the presence of functional FD in the population.

Best practice in primary care pathology: review 1

This first best practice review examines four series of common primary care questions in laboratory medicine, namely: (i) measurement and monitoring of cholesterol and of liver and muscle enzymes in patients in the context of lipid lowering drugs, (ii) diagnosis and monitoring of vitamin B12/folate deficiency, (iii) investigation and monitoring of paraprotein bands in blood, and (iv) management of Helicobacter pylori infection. The review is presented in a question-answer format, referenced for each question series. The recommendations represent a précis of guidance found using a standardised literature search of national and international guidance notes, consensus statements, health policy documents, and evidence based medicine reviews, supplemented by MEDLINE EMBASE searches to identify relevant primary research documents. They are not standards but form a guide to be set in the clinical context. Most are consensus rather than evidence based. They will be updated periodically to take account of new information.

Folic acid deficiency modifies the haematopoietic response to recombinant human erythropoietin in maintenance dialysis patients

BACKGROUND

While folic acid deficiency causes macrocytic anaemia in non-renal patients, the relevance of altered folate metabolism in anaemia of end-stage renal disease and its response to rHu-EPO is less clear.

METHODS

Ten haemodialysis patients with macrocytic anaemia due to dietary folic acid deficiency were compared to 10 matched (age, duration of dialysis, degree of anaemia) patients with normocytic normochromic anaemia. Nineteen patients received erythropoietin-alpha intravenously thrice weekly. The study design was a prospective crossover (ABA) comparison of the effects of intravenously administered high doses of folic acid on haemoglobin levels and EPO doses, with 6 months active supplementation (B) and two periods of 6 months duration each without folic acid supplementation (A).

RESULTS

The two patient groups did not differ at recruitment. Red blood cell folate levels were normal in patients with normocytic anaemia, but they were subnormal in all patients with macrocytic anaemia. Compared to the first period without folic acid supplementation, patients with macrocytic anaemia had significantly higher haemoglobin levels despite lower EPO doses after 6 months high-dose folic acid, and red cells had become normocytic. The removal of folic acid supplementation resulted in re-occurrence of macrocytosis and in a significantly lower response to rHu-EPO. In contrast, high-dose folic acid supplementation had no effect on response to rHu-EPO in patients with normocytic anaemia.

CONCLUSIONS

Folic acid deficiency may occur in elderly haemodialysis patients with poor dietary folate intake without regular oral supplementation and may cause hyporesponsiveness to rHu-EPO. Macrocytosis is a simple and cheap indicator for folate deficiency in end-stage renal disease patients on maintenance dialysis.

Is there a role for folate determinations in current clinical practice in the USA?

Our objectives were to determine the likelihood of true folate deficiency among patients tested for this disorder, to identify whether there were differences between the clinical indications for folate testing in folate-normal and folate-deficient patients and to assess the impact of a diagnosis of folate deficiency on patient management. The results of all blood samples analyzed for serum and erythrocyte folate levels during the year 2001 at the Cleveland Clinic Foundation were retrieved. Folate deficient patients were identified and their medical charts were reviewed to determine the indications, patient characteristics, and impact of this diagnosis on patient management. For comparison, medical chart review was also conducted on a control group composed of an equal number of randomly selected patients with normal serum folate values. A total of 6024 (4689 serum and 1335 erythrocyte) samples from 4985 patients were collected. In the study, 77 (1.6%) of the serum folate levels, from 74 patients, were identified as low. When compared with the control group, patients with low serum folate levels had lower hemoglobin and a greater red cell distribution width. Mean corpuscular volume, however, did not differ between the two groups. No significant differences in the clinical indications for serum folate level determinations could be identified. Only 39 of the 74 patients with low serum folate levels were given folate replacement, representing only 0.9% of the clinically suspected and tested patients. We conclude that determination of serum folate level infrequently led to appropriate folate replacement therapy. Moreover, even when suspected, true folic acid deficiency is rare and clinical indications are not helpful in diagnosis.