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.

Blood folate levels and risk of liver damage and hepatocellular carcinoma in a prospective high-risk cohort.

BACKGROUND: Studies in experimental animals suggest that low folate levels may play a role in liver damage and hepatocarcinogenesis. To examine this association in humans, folate levels in blood and risk for subsequent liver damage and hepatocellular carcinoma (HCC) were assessed in a population at high risk of liver cancer in China. METHODS: Four hundred fifteen hepatitis B surface antigen-positive participants of the Haimen City Cohort were prospectively followed between 1998 and 2002. Serum and RBC folate levels were determined at baseline. Alanine aminotransferase (ALT) and hepatitis B virus DNA levels were measured semiannually. Logistic regression modeling was used to examine the presence of hepatitis B virus DNA and HCC, whereas linear regression with a log-link function was used to examine ALT levels. RESULTS: There was a statistically significant inverse association between serum folate level and ALT level. ALT levels decreased with each quartile increase in serum folate (adjusted odds ratio, 0.86; 95% confidence interval, 0.76-0.97 for the highest compared with the lowest quartile; Ptrend = 0.002). After exclusion of three persons with prevalent HCC, 20 (4.9%) of the 412 study participants developed HCC during follow-up, with a median time between enrollment and HCC diagnosis of 2.66 years (interquartile range, 1.8-4.1). When comparing persons in the lowest quartile RBC folate to persons in all other quartiles, the analysis found that higher RBC folate levels were associated with reduced risk of hepatocarcinogenesis (odds ratio, 0.33, 95% confidence interval, 0.13-0.86; P(trend) = 0.02). CONCLUSIONS: This study suggests that increased folate levels in humans may be inversely associated with the development of liver damage and HCC.

International Standard for serum vitamin B(12) and serum folate: international collaborative study to evaluate a batch of lyophilised serum for B(12) and folate content.

BACKGROUND: Vitamin B(12) and folate measurements in serum show wide inter-methodology variability. This variability appears to be due in part to the lack of standardisation against internationally accepted reference materials. Pooled human serum, lyophilised in ampoules and designated 03/178, was therefore evaluated by 24 laboratories in seven countries for its suitability to serve as an International Standard (IS) for B(12) and folate. METHODS: IS 03/178 was assayed using a range of commercial analysers, microbiological assays and, for folate, candidate reference methods based on liquid chromatography coupled to isotope-dilution tandem mass spectrometry (LC/MS/MS). RESULTS: Mean vitamin B(12) and folate values for reconstituted 03/178 across all laboratories and methods were 480 pg/mL [coefficient of variation (CV) 12.8%] and 5.52 ng/mL (CV 17.1%), respectively. The total folate content of reconstituted 03/178, determined using LC/MS/MS, was 12.1 nmol/L (equivalent to 5.33 ng/mL), made up of 9.75 nmol/L 5-methyl tetrahydrofolic acid (5MeTHF; CV 5.5%), 1.59 nmol/L 5-formyl tetrahydrofolic acid (5FoTHF; CV 4.2%) and 0.74 nmol/L folic acid (FA; CV 31.6%). The inclusion of three serum samples in the study with different B(12) and folate levels demonstrated a considerable reduction in inter-laboratory variability when the B(12) and folate content of the samples was determined relative to the IS 03/178 rather than to the analyser calibration. IS 03/178 demonstrated satisfactory long-term stability in accelerated degradation studies. CONCLUSIONS: Use of IS 03/178 to standardise serum B(12) and folate assays reduced inter-laboratory variability. The World Health Organization (WHO) Expert Committee on Biological Standardisation established 03/178 as the first IS for serum vitamin B(12) and serum folate, with assigned values of 480 pg/mL of vitamin B(12) and 12.1 nmol/L folate when the lyophilised contents of the ampoule are reconstituted with 1 mL of water.