Metabolite assays in cobalamin and folate deficiency

Cbl and folate are both necessary for the metabolism of HCYS, whereas only Cbl is required for MMA metabolism. During the past decade, analytical methods have been developed that are sensitive enough to detect low levels of MMA and HCYS normally present in the plasma. These methods are sufficiently precise to be used in the clinical laboratory and measurements of the serum levels of the metabolites provide sensitive and specific techniques for the identification of Cbl and folate deficiencies. These techniques constitute an important addition to the battery of diagnostic tests that are available for detecting the vitamin deficiencies and for distinguishing each from the other. By virtue of the role of Cbl and folate in the metabolic pathways that involve MMA and HCYS, levels of both metabolites rise in Cbl deficiency, but only HCYS rises in folate deficiency. During the development of Cbl or folate deficiencies, accumulation of these metabolites in the plasma signals the existence of a condition of biochemical vitamin deficiency of sufficient degree to cause impairment in the metabolic pathways which are dependent on these vitamins. Circulating metabolite levels appear to accurately reflect the nutritional status of the vitamins and a rise in serum metabolite levels is therefore one of the earliest and most reliable indicators of developing Cbl and folate deficiencies. Elevations of serum metabolites above the reference range not only precede a fall in the serum vitamin levels but also show a more consistent correlation with objective evidence of vitamin deficiency than do low blood vitamin levels. The advent of serum metabolite measurements has also made it possible to identify subtle or atypical forms of vitamin deficiency that may be associated with unusual or previously undiscovered disease manifestations. Thus, in patients who display only neurological manifestations of disease, underlying Cbl deficiency may be revealed by the finding of raised serum or urine levels of MMA. Similarly, unsuspected folate deficiency may be disclosed by the finding of a raised serum HCYS. This may have important implications with respect to disease risk, since there is mounting evidence that sub-optimal folate nutritional status may be associated with increased risks of vascular disease, neoplasia and birth defects. Finally, the measurement of serum levels of MMA, HCYS and other metabolites that accumulate in Cbl and folate deficiencies may provide important new insights into the mechanism whereby these vitamin deficiencies lead to different patterns and manifestations of disease.

Folate metabolism and neural tube defects: a review

The importance of folate in normal fetal development and wellbeing has been recognized only during the past three decades and knowledge concerned is still far from complete. In man, folate acts as a substrate in the transfer of one-carbon moieties and thereby, plays an essential role in the synthesis of several amino acids such as methionine and nucleic acids. Consequently, folate requirements are related to the amount of tissue growth. Epidemiological, clinical and teratological research showed that this B-vitamin is particularly involved in the prevention and pathogenesis of neural tube defects. Therefore, in this review the metabolism of folate has been outlined. Furthermore, the characteristics of the various genically determined folate 'deficiencies' as well as a possible biochemical explanation of the relationship between folate and neural tube defects are being discussed. Finally, the new recommendations launched in November 1993 by the Dutch Health Council as well as the Food and Nutrition Council with regard to folate supplementation in the prevention of neural tube defects are presented.

Deficiency testing for iron, vitamin B12 and folate

Dietary cells and the vitamins B12 and folate are necessary for the production of the red blood cells (erythrocytes), which carry oxygen from the lungs to the tissues and carbon dioxide from tissues to lungs. Deficiency of either one results in anaemia, which is characterised by low haemoglobin concentration. Symptoms result from reduced tissue oxygenation and include weakness, lethargy, palpitation, headache and shortness of breath. The first-time laboratory test of all patients suspected of being anaemic is the full blood count. Results of a full blood count may suggest the anaemia is caused by a nutritional deficiency of B12 folate or iron. Laboratory measurement of the concentration in blood of iron and vitamin B12 and folate, along with several other tests described here, are useful in the differential diagnosis of the anaemic patients.

Anemia in pregnancy

Anemia is the most common hematologic complication of pregnancy and is associated with increased rates of premature birth, low birth weight and perinatal mortality. Iron deficiency is the most common cause of anemia, and most pregnant women benefit from daily supplementation of 30 to 60 mg of elemental iron. Folic acid deficiency, the most common cause of megaloblastic anemia in pregnancy, is associated with open neural tube defects and other complications. It is recommended that daily supplementation with 4 mg of folic acid be started at least one month before conception and continued through the first trimester. Other less common causes of anemia include glucose-6-phosphate dehydrogenase deficiency, sickle cell trait and disease, and the thalassemias. The primary care provider should emphasize risk evaluation, dietary and preconceptual counseling, testing and appropriate treatment.

Possible folate deficiency with postsurgical infection

A 51-year-old obese woman was transferred to our hospital for management of a complicated laparoscopic cholecystectomy accompanied by fever and malaise. A liver abscess was discovered. On postoperative day 52 it was noted that the patient's tongue was magenta and sore and that she had altered taste, pallor, severe weight loss, diarrhea, and poor appetite and mood. A dermatology consult suggested that her tongue abnormalities were most likely nutrition-related, and a hematologic blood smear was suggestive of folate deficiency. Premorbidly, the patient had consumed a diet chronically low in folate and had received estrogen therapy for 15 years. Throughout the patient's hospitalization, she had bouts of fever and received numerous antibiotics. Within a month of initiating nutrition support and vitamin/mineral supplements, her nutritional status improved dramatically. This patient's poor diet, long-term estrogen use, surgical stress, infection, and lack of early nutrition support may have contributed to her possible folate deficiency and her prolonged hospital stay.

Plasma homocysteine in relation to serum cobalamin and blood folate in a psychogeriatric population

Plasma homocysteine, serum cobalamin and blood folate were analysed in 296 consecutive patients referred to a psychogeriatric department for diagnosis of mental disease. Plasma homocysteine correlated with positive significance with age and serum creatinine, and with negative significance with serum cobalamin and blood folate. Approximately 35-40% of the patients with low serum cobalamin (< 150 pmol l-1) or low blood folates (< 150 nmol l-1) exhibited normal values of plasma homocysteine (< 19.9 mumol l-1). Possibly, these patients do not have a deficiency of the vitamins in the tissue. At least 7.5% of the patients with serum cobalamin levels (> 150 pmol l-1) showed an inexplicably increased level of plasma homocysteine. These patients might have a deficiency of tissue cobalamin despite the normal serum cobalamin levels. The effect of cobalamin supplementation for 7-10 days on plasma homocysteine was tested in 62 patients with different levels of serum cobalamins. We found the most pronounced decrease of plasma homocysteine in the patients with lowest serum cobalamin levels and in the patients with highest plasma homocysteine, indicating that the percentage decrease of the initial concentration of plasma homocysteine could reflect the degree of cobalamin deficiency. Folate supplementation for 7-10 days reduced plasma homocysteine not only in patients with folate deficiency but also in those with a normal folate status, and even in patients with cobalamin deficiency. The latter patients further reduced their plasma homocysteine after additional cobalamin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Discriminant analysis of macrocytic red cells

Laboratory classification of red cell disorders uses the red cell indices (MCV, MCH, MCHC, RDW) and information gleaned from microscopic evaluation of a blood film. Additional red cell information is now available using the H series of automated blood cell analysers (Ames Technicon Division of Bayer Diagnostics). This study involved the development of a discriminant rule which would differentiate between three causes of macrocytosis (vitamin B12/folate deficiency, alcohol excess/liver disease and a reticulocytosis) using the information available on Research Screen 1 and Report Screen 3 of the H*1 instrument (Report Screen 3 is a graphical display of the trimmed scattergram of red cell volume and red cell haemoglobin concentration and Research Screen 1 displays the associated numerical data). Three methods of analysis were assessed to define a suitable discriminant rule. The percentages of patients correctly classified by the three methods were: 92.1%, 82.0% and 89.2% for Methods 1, 2 and 3 respectively. Method 1 involved the application of quadratic discrimination to transformed variables and produced the best results. Although complex, it could easily be applied using the microprocessor capability of the average multiparameter haematology analyser.

Malnutrition: folate and cobalamin deficiency

Malnutrition of folate and cobalamin occurs on a world-wide scale. Millions of individuals, for a variety of cultural, religious and socio-economic reasons, ingest less than the daily amounts required to maintain body stores. Assessment of intake depends on the population under study, method of food preparation and assay technique. Up to 90% of folate may be destroyed by cooking and, although less, significant amounts of cobalamin can also be lost in this way. Estimates of the proportion of both vitamins absorbed from a mixed diet vary, but may be as little as 50%. The need for supplementation is more common with folate than cobalamin. However, recent advances have highlighted subtle sub-clinical metabolic changes in some groups, particularly the elderly. Further investigation into their requirements is indicated. New assays for metabolites of cobalamin and folate are highly sensitive but lack specificity and are not readily available.

Elevated serum homocysteine as a predictor for vitamin B12 or folate deficiency

Tissue deficiency of vitamin B12 and folate results in an increase in serum homocysteine (sHcy). We have measured sHcy in patients with reduced serum vitamin B12 and/or red cell folate (RCF) to determine its usefulness as a discriminant for the diagnostic interpretation of reduced vitamin levels. Of 3846 patients who had serum vitamin B12 and RCF assayed, 335 (9%) had reduced vitamin levels. Multivariate analysis showed a significant association between sHcy and serum creatinine (p = 0.0001), positive intrinsic factor (IF) antibody or neutrophil hypersegmentation (NHS) (p = 0.001), increased MCV (p = 0.014) and low RCF (p = 0.025) but no relationship with the level of serum vitamin B12 or haemoglobin. After censoring the patients with renal impairment (n = 54), the distribution of the remaining 72 patients with elevated sHcy was 37/151 (25%) with low serum vitamin B12 with or without low RCF and 35/130 (27%) with low RCF alone. sHcy correctly identified response to vitamin therapy in 33/35 (94%) patients who had adequate parameters to assess response. The positive predictive values of IF antibody/NHS, macrocytosis and/or low RCF for elevated sHcy were 100% and 34% respectively. Twenty-four percent of patients with a low serum vitamin B12 and elevated sHcy had no abnormal haematologic parameters as determined by the routine laboratory staff. These data suggest that the usefulness of measuring sHcy in a routine diagnostic setting is limited and a careful review of the peripheral blood for macrocytosis and NHS plus determination of RCF may be a more cost-effective process than sHcy assay in most instances to determine the presence of tissue deficiency.

[Macrocytic anemia in the last trimester of pregnancy due to dietary insufficiency--initially interpreted as the HELLP syndrome]

A case of severe macrocytic anaemia caused by cobalamin and folic acid deficiency in a 32 year-old gemellipregnant woman in gestational week 32 +2 is described. Her symptoms and the laboratory data were initially interpreted as HELLP-syndrome (haemolysis, elevated liver enzymes and low platelet count), and caesarean section was performed. None of the persons involved in her earlier prophylactic controls suspected anaemia, and no specific dietary advice were given. If she had received dietary advice early in the pregnancy, anaemia could have been avoided. This emphasizes the need for dietary advice early in pregnancy.

Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies

PURPOSE

Patients with cobalamin (vitamin B12) deficiency usually lack many of the classic features of severe megaloblastic anemia; because of the low diagnostic specificity of decreased serum cobalamin levels, demonstrating the deficiency unequivocally is often difficult. We examined the sensitivity of measuring serum concentrations of methylmalonic acid and total homocysteine for diagnosing patients with clear-cut cobalamin deficiency and compared the results with those of patients with clear-cut folate deficiency.

PATIENTS AND METHODS

Serum metabolites were measured for all patients seen from 1982 to 1989 at two university hospitals who met the criteria for cobalamin and folate deficiency states and for such patients seen from 1968 to 1981 from whom stored sera were available. In all, 406 patients had 434 episodes of cobalamin deficiency and 119 patients had 123 episodes of folate deficiency. Criteria for deficiency states included serum vitamin levels, hematologic and neurologic findings, and responses to therapy. Responses were documented in 97% of cobalamin-deficient patients and 76% of folate-deficient patients. Metabolite levels were measured by modified techniques using capillary-gas chromatography and mass spectrometry.

RESULTS

Most of the cobalamin-deficient patients had underlying pernicious anemia; two thirds were blacks or Latinos. Hematocrits were normal in 28% and mean cell volumes in 17%. Of the 434 episodes of cobalamin deficiency, 98.4% of serum methylmalonic acid levels and 95.9% of serum homocysteine levels were elevated (greater than 3 standard deviations above the mean in normal subjects). Only one patient had normal levels of both metabolites. Serum homocysteine levels were increased in 91% of the 123 episodes of folate deficiency. Methylmalonic acid was elevated in 12.2% of the folate-deficient patients; in all but one, the elevation was attributable to renal insufficiency or hypovolemia.

CONCLUSIONS

For the cobalamin-deficient patients, measuring serum metabolite concentrations proved to be a highly sensitive test of deficiency. We conclude that normal levels of both methylmalonic acid and total homocysteine rule out clinically significant cobalamin deficiency with virtual certainty.

Use of red blood cell indices (MCV, MCH, RDW) in monitoring chronic hemodialysis patients treated with recombinant erythropoietin

Human recombinant erythropoietin (rHu-Epo) is now extensively used in chronic renal failures; this treatment, resulting in a correction of the severe anemias seen in hemodialysed patients, may in turn lead to a resistance to rHu-Epo therapy by reason of the shortage of erythropoiesis factors, such as iron, vitamin B12 and folates. The utility of the red cell indices (MCV, MCH, RDW) for detection of early iron, folate and B12 deficiencies was studied in eighteen hemodialysed patients with end-stage renal failure treated with rHu-Epo; Microcytosis (MCV < 80 fl) was found ineffective in detecting iron deficiencies as well as macrocytosis (MCV > 100 fl) in folate and B12 deficiencies, partly due to the high incidence of associated iron and folate deficiencies. Lowered MCH (< 27 pg) was not more efficient than microcytosis in detecting early iron deficiencies. Increased RDW was the most sensitive feature for folate, iron and B12 deficiencies with respective sensitivities of 62.5%, 72% and 75%. The global specificity for detecting all deficiencies was 74%. However, high RDW values were not indicative of any type of deficiency; it may thus be concluded that RDW is a non expensive, non invasive and sensitive test, which allows a selection of hemodialysed patients treated with rHu-Epo for a complete investigation program, in order to detect early iron, B12 and folate deficiencies.

[Erythrocyte mean corpuscular volume of psychiatric patients]

It has been observed clinically that the mean corpuscular volume (MCV) of erythrocytes is increased in psychiatric patients, but this phenomenon has not been investigated. We therefore compared the MCV of 177 patients in our psychiatric day care ward and in our psychiatric outpatient clinic. The MCV of these psychiatric patients, and especially that of the outpatients, were significantly greater than that of normal controls. No association was found between MCV and sociodemographic or clinical variables. The sensitivity of a high MCV level as a diagnostic for folic acid deficiency was 42.9%, with a specificity of 80.6%. The sensitivity of a high MCV level as a diagnostic for vitamin B12 deficiency was 23.1%, with a specificity of 79.4%.

[Folic acid supply in pregnancy--results of a prospective longitudinal study]

After discussing the problem of folic acid requirements and supply during pregnancy, the results of a longitudinal study on 162 pregnant women are presented. By measuring biochemical and morphological changes in two subgroups (non-substituted vs unspecifically substituted), the necessity of a substitution with folic acid is discussed, as there might be additional requirements for the pregnant and the foetal organism. Concentrations of folic acid in the maternal plasma and in the erythrocytes as well as the segmentation rate and hypersegmentation of the granulocytes show a clear decrease in pregnancy. At the same time there was a significant difference between the subjects substituted and not substituted; the foetus and newborn levels were much higher than their mothers' concentrations. Moreover, there was a correlation between red cells folic acid levels in the last trimester and duration and outcome of pregnancy. These results indicate a substitution with folic acid for certain populations in pregnancy, which are highlighted.

Folate, vitamin B12 and cognitive impairment in patients with Alzheimer's disease

This study examines the relationship between folate, vitamin B12 and severity of cognitive impairment in patients with Alzheimer's disease (AD) as compared with other disorders associated with cognitive impairment. The patients were 97 consecutive referrals to an AD clinic. Forty patients had either possible or probable AD, 31 had other dementias (OD) and 26 had mild cognitive impairment (cognitively impaired, not demented; CIND). Patients had blood drawn for serum, red cell folate and B12, as well as other biochemical indicators of nutrition, within 24 h of the Mini-Mental State Examination (MMSE). In the AD group, only B12 was significantly correlated with MMSE. Using regression analysis, B12 contributed significantly to variance in MMSE. There was no correlation between MMSE and serum, red cell folate or B12 in the OD or CIND group and no significant correlation between MMSE and other nutritional indices in any group. These findings suggest the possibility of a specific relationship between B12 levels and severity of cognitive impairment in patients with AD.

Folates and post partum depression

Hypofolatemia can cause psychiatric disturbances of a depressive nature. Pregnancy and delivery are often associated with hypofolatemia. This study was conducted to determine if hypofolatemia at day 3 post partum is a risk factor for baby blues or post partum depression. To study this hypothesis, 131 post partum women were followed prospectively for the 3 months immediately following delivery. 19% were found to have 'baby blues', as defined by a score greater than 20 on Pitt's scale (Pitt, 1968, J. Psychiatry 114, 1325-1335) and 12% had post partum depression as defined by a score greater than 7 on QD2A scale (Pichot et al., 1984, Rev. Psycholog. App. 34, 229-250, 323-340), within the three months post partum. No relationship was observed between the serum or erythrocyte folate levels on the third day following delivery and the maternal post partum depression scores. A statistically significant correlation between post partum depression and previous psychiatric disturbance was, however, observed.

[Nutritional status of elderly patients at admission to a general psychiatric hospital. An inventory]

The nutritional status of 121 psychiatric patients over the age of 60 years was examined on admission in a general psychiatric hospital. Before admission all patients were living independently. They were admitted directly from their homes. We found that the older psychiatric patient is evidently at risk for malnutrition. A quarter of the males had, according to the Quetelet's index, a low weight. Half of the males and one third of the females had a thiamin-deficiency, whereas half of all patients showed a deficiency of folic acid. Furthermore, in half of the males and one tenth of the females anaemia was diagnosed. Widowers and to a lesser extent also patients with an organic brain disease or psychotic disturbance ran a greater risk of malnutrition in comparison to their fellow patients. A relation between behaviour, measured by the Nosie (Nursing Observation Scale for Inpatient Evaluation) and the nutritional status was not found.

[Clinical evaluation of anemia in the aged]

Of 533 patients over 65 years old (153 males and 380 females), admitted to geriatric units for various medical diseases, 111 (20.8%) were anemic. Among males the prevalence of anemia was 30.1%, among females 17.1%. Three principal causes of anemia were revealed. The most frequent (42.3%) was microcytic, hypochromic anemia, with low levels of serum iron concentrations, related to gastrointestinal diseases (with chronic occult blood loss). 38.7% of anemic elderly people was affected by chronic diseases. In 19.0% a folate (16 case) and iron (5 cases) deficiency was revealed. These results suggest that anemia in the elderly is always pathological; hemoglobin values lower than 12 g/dl should be considered abnormal and investigated.

[Case report of a nutrition-induced anemia due to folic acid deficiency]

Because of anaemia and dystrophy a girl was admitted to hospital. By bone marrow aspiration the diagnosis of a megalocytic anaemia was established. The determination of folic acid revealed a severe folate deficiency caused by education problems with consecutive malnutrition. Under folic acid replacement therapy and intensive talks with the parents the girl recovered from her illness and after change of nutrition she developed well without any further folic acid replacement.