The interpretation of prolactin results is difficult as race related reference intervals are scarce, especially in Nigerian women. Serum prolactin reference intervals were determined from 120 subjects. Subjects were randomly selected from antenatal clinics and general outpatient clinics in one private hospital and three government hospitals in Zaria, Northern Nigeria. They consisted of six groups made up of women that were A-non pregnant, B-first trimester of pregnancy, C-second trimester of pregnancy, D-third trimester of pregnancy, E-labour, and F-puerperium. Their blood samples were collected via venipuncture between 09.00 and 13.00 h after which they were centrifuged and the sera stored at -8°C for further analysis. The samples were analyzed at the Department of Chemical Pathology, Ahmadu Bello University Teaching Hospital, Shika. Serum prolactin was determined with Prolactin quantitative test kits using the principle of solid phase enzyme-linked immunosorbent assay. The concentration of prolactin is proportional to the color intensity of the samples as measured spectrophotometrically at a wavelength of 450 nm. Informed consent and ethical clearance was obtained before commencement of the study. Results were presented as mean ± standard deviation (SD) and data analyzed using one-way analysis of variance, while post-hoc test was carried out. A level of significance of p<0.05 was considered statistically significant, while the reference range was defined as 95% confidence interval. Serum prolactin results showed a significant increase in pregnant women as compared to the non-pregnant, not lactating subjects (20.24±3.41 ng/ml; 95% Confidence Interval (CI): 18.84-21.65 ng/ml). There were also significant trimester related differences in serum prolactin with prolactin levels increasing during the first trimester though not significantly (29.84±5.08 ng/ml). A sharp increase was observed during the second trimester (96.09±18.82 ng/ml; 95% CI: 89.41 to 102.76 ng/ml). There was a further increase at the third trimester (171.11±32.92 ng/ml; 95% CI: 159.03-183.18 ng/ml), a peaking during labour (198.37±15.81 ng/ml; 95% CI: 186.22-210.52 ng/ml) with a significant decline during the first week of the puerperium (197.19±22.11 ng/ml; 95% CI: 183.83-210.55 ng/ml). Apparent changes in serum prolactin levels were similar to that of previous studies; although the ranges for all groups were observed to be narrower as compared to those of other studies.
Key words: Serum prolactin, reference ranges, enzyme immunoassay, Zaria.
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