Laboratory assessment of iron status in pregnancy.

BACKGROUND: Efforts to improve maternal nutrition during pregnancy prompted an observational study of the occurrence of maternal iron deficiency and its laboratory diagnosis in almost 500 pregnancies. METHODS: In this longitudinal study, the biochemical and haematological iron indices of women (n=492) attending a prenatal clinic in a Dublin maternity hospital were assessed at first booking (mean 15.9 weeks), and after 24 weeks, and 36 weeks of gestation. Full blood counts were measured. Serum ferritin (SF), zinc protoporphyrin (ZPP), and transferrin receptor (sTfR) concentrations were assayed and transferrin receptor index (sTfR-Index) was calculated. The occurrence of low values and their diagnostic values were considered. RESULTS: A high occurrence iron deficiency (ID) at first booking (SF<12 µg/L) had increased over six-fold by 24 weeks, and all biochemical iron indices reflected progressive iron depletion right up to term. The WHO recommended anaemia "cut-off" (Hb<110 g/L) was insensitive to biochemical iron deficiency at booking, missing over 90% of the low SF values (SF<12 µg/L) which were mostly associated with much higher Hb levels. CONCLUSIONS: This study stresses the importance of including a biochemical index of iron status in prenatal screening and supports SF as the best indicator of biochemical ID overall. sTfR was insensitive to iron deficiency in early pregnancy, whereas the sTfR-Index, as a ratio, has the potential to distinguish between ID and physiological anaemia, and may offer stability in the assessment of iron stores from early pregnancy to full term. A policy of early screening of both Hb and SF concentrations is recommended as the minimum requirement for surveillance of maternal iron status in pregnancy.

A dried serum spot assay for vitamin B(12).

BACKGROUND: A newly developed dried serum spot (DSS) vitamin B(12) assay compares well with a conventional reference serum vitamin B(12) microbiological assay (r=0.97, n=161) and demonstrates adequate within (CV% <6) and between assay (CV% <10) reproducibility. METHODS: The consistency of long-term vitamin B(12) assay performance was supported and validated using a reconstituted International Reference Serum (IRR 81/563) stored at -70 degrees C as both whole serum aliquots and as DSS. The inclusion of such reference sera also allows accurate comparisons to be made with data from other laboratories and studies. RESULTS: The DSS matrix displays excellent characteristics of pre-analytical serum vitamin B(12) stability at ambient temperatures with less than 5% loss of activity occurring at 4 degrees C, 20 degrees C and 37 degrees C after 7 days of storage in the dark. CONCLUSIONS: These qualities underline the suitability of the DSS matrix for epidemiological screens of serum vitamin B(12) levels by obviating the need for costly refrigeration and specialised handling of serum samples and allowing economic transportation using the basic postal service.