Evaluation of a commercial radioassay for the simultaneous estimation of vitamin B12 and folate, with subsequent derivation of the normal reference range

Níveis de ácido fólico sérico em lactentes eutróficos, alimentados com leite materno, leite de vaca ou fórmula modificada

OBJETIVO: Verificar os níveis de ácido fólico em três grupos de lactentes e comparar os valores encontrados; avaliar a necessidade de suplementação dessa vitamina aos quatro meses, quando as reservas teciduais são escassas e as fontes dietéticas pobres em folatos, em um período no qual a alimentação é exclusivamente láctea. MÉTODOS: Foram analisados os níveis de ácido fólico sérico, obtidos pelo método de radioimunoensaio, em 120 lactentes eutróficos, aos quatro meses, com alimentação láctea exclusiva, sendo 40 com aleitamento materno, 40 com leite de vaca pasteurizado e fervido e 40 com fórmula láctea industrializada e enriquecida com ácido fólico. RESULTADOS: Os níveis de ácido fólico sérico nos lactentes alimentados exclusivamente com leite de vaca pasteurizado e fervido foram significativamente menores do que os dos lactentes alimentados com leite materno e os alimentados com fórmula láctea modificada, enriquecida com folatos. Estes dois últimos grupos não mostraram diferenças entre si. CONCLUSÕES: O estudo ressalta a necessidade de suplementação de ácido fólico nos lactentes aos quatro meses alimentados exclusivamente com leite de vaca. A pasteurização e a fervura do leite de vaca, habitualmente utilizadas, levam à deficiência dessa vitamina, tão importante na nutrição humana.

The use of radioisotopes in haematology

Radioisotopes used in haematology may be divided into four groups: 1. those used for in vivo studies, involving the labelling of cells in the blood or bone marrow and the use of labelled plasma albumin; 2. investigations involving surface counting over organs such as the bone marrow, spleen, liver and heart; 3. in vitro use of radioisotopes in the haematology laboratory and 4. isotopes used as part of imaging procedures. The shorter the half life of the isotope, the more limited patient exposure to radioactivity will be, but the greater the problems of starting and completing the investigation before the isotope has decayed. Isotopes studies should not be carried out in children or pregnancy unless there are exceptional clinical indications.

Laboratory diagnosis of megaloblastic anaemia: current methods assessed by external quality assurance trials

The results of an Interregional quality assurance scheme for tests in the diagnosis of megaloblastic anaemia were reviewed to assess the methods used. Serum folate assays showed great variation between methods, partly due to limitations in assessment by external quality assurance. Red cell folate assays yielded widely different results and much imprecision due both to the differences in preparation of the haemolysate and to the problems inherent in radioassay of a mixture of folate compounds. Intrinsic factor antibody tests showed appreciable variation in sensitivity. There was considerable inconsistency in the detection of polymorph nuclear hypersegmentation.

Factors influencing haematological measurements in healthy adults

By studying 516 healthy adults normal reference intervals were established for the Coulter "S" haematological indices with the plasma ferritin, B12, folate and red cell folate in a subgroup of 306. Significant sex related differences were found for all measurements other than MCV, MCH and B12. After allowing for these sex related differences, the effects of age, body size, fasting, smoking, alcohol, exercise and contraceptive pill usage on the parameters studied was defined.

Marathon Running Fails to Influence RBC Survival Rates in Iron-Replete Women

In brief: As many as 80% of female long-distance runners show iron deficiency. One explanation is RBC fragmentation due to mechanical trauma. In this study, radiolabeling was used to measure RBC survival rates in six iron-replete female marathon runners. In addition, tests for urinary hemosiderin were conducted in a search for secondary evidence of RBC damage. Radioactivity counts on blood samples drawn before and after a standard 26-mile marathon failed to disclose traumatic RBC fragmentation, and the tests for urinary hemosiderin were negative. Other possible factors in iron deficiency, such as diet, therefore merit consideration.