Population-Based Biochemistry, Immunologic and Hematological Reference Values for Adolescents and Young Adults in a Rural Population in Western Kenya

Abstract

BackgroundThere is need for locally-derived age-specific clinical laboratory reference ranges of healthy Africans in sub-Saharan Africa. Reference values from North American and European populations are being used for African subjects despite previous studies showing significant differences. Our aim was to establish clinical laboratory reference values for African adolescents and young adults that can be used in clinical trials and for patient management.Methods and FindingsA panel of 298, HIV-seronegative individuals aged 13–34 years was randomly selected from participants in two population-based cross-sectional surveys assessing HIV prevalence and other sexually transmitted infections in western Kenya. The adolescent (<18 years)-to-adults (≥18 years) ratio and the male-to-female ratio was 1∶1. Median and 95% reference ranges were calculated for immunohematological and biochemistry values. Compared with U.S-derived reference ranges, we detected lower hemoglobin (HB), hematocrit (HCT), red blood cells (RBC), mean corpuscular volume (MCV), neutrophil, glucose, and blood urea nitrogen values but elevated eosinophil and total bilirubin values. Significant gender variation was observed in hematological parameters in addition to T-bilirubin and creatinine indices in all age groups, AST in the younger and neutrophil, platelet and CD4 indices among the older age group. Age variation was also observed, mainly in hematological parameters among males. Applying U.S. NIH Division of AIDS (DAIDS) toxicity grading to our results, 40% of otherwise healthy study participants were classified as having an abnormal laboratory parameter (grade 1–4) which would exclude them from participating in clinical trials.ConclusionHematological and biochemistry reference values from African population differ from those derived from a North American population, showing the need to develop region-specific reference values. Our data also show variations in hematological indices between adolescent and adult males which should be considered when developing reference ranges. This study provides the first locally-derived clinical laboratory reference ranges for adolescents and young adults in western Kenya.

Laboratory Reference Intervals in Africa

“…(MCH) by gender have been observed in several African studies, with adult males having higher values than adult females in East Africa [9,16,20,31,39,40], Southern Africa [20,36], West Africa [41] and Central Africa [42]. These gender differences in RBC parameters as illustrated in our findings (Table 2), are consistent with previously established evidence that males have higher values than females for these parameters and is partly attributed to the influence of the androgen hormone on erythropoiesis [43,44] and to menstrual blood loss in women [16,25,39,42,45].…”

“…In our study [9] of adolescents and adults living in rural western Kenya, all participants were screened by a review of medical history, a physical examination, tested for HIV and pregnancy (for females), and treated for any illnesses diagnosed. Participants were included if they were a permanent resident of the study area, between 13 and 34 years of age and able to provide informed consent or assent if a minor.…”

“…The normal values of red cell counts and indices (i.e., hemoglobin concentration, hematocrit, mean corpuscular volume, red blood cell count), white cell counts and platelet counts are known to vary with age, sex and pregnancy [9,16,20,31,36]. In addition, genetic and environmental factors can also affect the reference intervals in certain populations [32][33][34]37].…”

“…African RBC component values were significantly lower when compared to reference intervals obtained from the Massachusetts General Hospital [6] from a North American population, and thus a significant proportion are misclassified when the NIH DAIDS toxicity tables are applied [9,34,38]. Differences observed in the RBC components between African and Caucasian populations may be attributed to lower dietary iron intake, genetic polymorphisms such as thalassemia and sickle cell trait or chronic exposure to endemic parasites including helminths, malaria and schistosomiasis.…”

“…Despite this, clinicians and researchers in Africa have continued to use reference values of European or North American populations. Our group in Kenya has recently published reference intervals based on the CLSI guidelines and are currently assisting regional laboratories to establish their own reference intervals [9].…”