Reference intervals for common chemistry and haematology laboratory tests in a healthy Kenyan population: variation with age, sex, BMI and comparison with a South African
Date
2020-12
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Abstract
ENGLISH ABSTRACT: Introduction
Laboratory results play an important role in assessment of one’s health status including detection of sub-clinical disease. Reference intervals (RIs) have been shown to vary across different populations due to various reasons including ethnic and racial differences, differences in reference populations and statistical approaches used in deriving the RIs. The International Federation of Clinical Chemistry committee on reference intervals and decision limits has been carrying out a global study aimed at harmonizing RIs. Kenya is the only country in East Africa that participated in this study and therefore the derived RIs will serve as a reference point for laboratories in the region. It is also important to identify what factors cause variations in RIs and whether partitioning based on age or sex will make them more specific. We subsequently compared our RIs with those from South Africa also derived as part of the global RI study.
Methods
Recruitment of study participants in Kenya was carried out between January and October 2015 in several counties after obtaining informed consent. Inclusion of participants was limited to healthy adults aged 18-65 years stratified into 4 age groups: 18-29, 30-39, 40-49 and 50-65 years. Haematology tests were performed at the PathCare laboratories in Nairobi, Kenya while all other analysis was done at the PathCare reference laboratory in Cape Town, South Africa. For purposes of the global RI study, all participating laboratories received a panel of sera that had assigned values to enable recalibration of reference values (RVs) and alignment across different countries. RIs were determined using both parametric and non-parametric methods before and after applying the latent abnormal values exclusion (LAVE) method.
Results
Out of 596 volunteers, 533 met the inclusion criteria: 260 (48.8%) males and 273 (51.2%) females. The prevalence of metabolic syndrome (MetS) was 25.6% and less than 1% of participants had reduced estimated glomerular filtration rate (eGFR). Sex-specific RIs were required for uric acid, creatinine, total bilirubin (TBil), total cholesterol (TC), transaminases, transferrin, transferrin saturation and immunoglobulin-M. Age-specific RIs were required for glucose and triglyceride for both sexes, and for urea, magnesium (Mg), TC, HDL-cholesterol ratio, alkaline phosphatase (ALP), and ferritin for females. Kenyan RIs were comparable to those of other countries participating in the global study with a few exceptions such as higher ULs for TBil and c-reactive protein (CRP). South African RIs for uric acid, TC, low density lipoptotein cholesterol, alanine transaminase, lactate dehydrogenase, ALP, albumin, Mg, thyroid stimulating hormone and prostate specific antigen were lower than the Kenyan RIs.
Conclusion
Kenyan RIs for several analytes were established using a harmonized protocol from well-defined reference individuals. Given the rigour with which the study was conducted, the derived RIs will provide a useful reference for laboratories in sub-Saharan Africa that are looking for RIs for common haematology and biochemistry tests. For most analytes, harmonization of RIs between Kenyans and South Africans of African ancestry was not possible as they could result in misclassification of individuals as either diseased or healthy given the differences seen.
AFRIKAANS OPSOMMING: Inleiding Laboratorium uitslae speel ‘n belangrike rol in die behandeling en diagnose van onderliggende siektes in pasiente. Normale reikwydtes (NW) vertoon verskillend oor bevolkingsgroepe om verskeie redes: etniese- en verwysings polulasie verskille asook verskillende statistiese metodes wat gebruik word. Die Internationale Federasie van Kliniese Chemie se kommitee vir reikwydtes en bepalings limiete koördineer ‘n globale projek om te bepaal of NW geharmoniseer kan word of nie. Kenya was die enigste land in Oos Afrika wat aan die globale projek deegeneem het. Kenya NW’s kan dien as verwysingsraamwerk vir ander laboratoria in die streek. Dit is belangrik in studies van hierdie aard om te bepaal watter faktore variasies in NW sal veroorsaak en die noodsaklikheid om ‘n skeiding te maak in NW om dit spesifiek te maak vir ouderdom en geslag. Hierdie studie het die NW van Kenya met die van Suid Afrika (RSA) vergelyk wat ook deegeneem het aan die globale projek. Metode Werwing van deelnemers in diè studie was gedoen in verskeie graafskappe in Kenya tussen Januarie en Oktober 2015 met ingeligte toestemming. Gesonde deelnemers was toegelaat om deel te neem tussen 18 – 65 jarige ouderdom, met verdere subverdeel in 4 verskillende ouderdomsgroepe: 18 – 29, 30 – 39, 40 – 49 en 50 – 65. Haematologiese analise van bloedmonsters was gedoen by PathCare Laboratorium in Nairobi, Kenya. Alle ander analise was gedoen was by PathCare se Verwysingslaboratorium in Kaapstad, RSA. Vir die doeleindes van die globale studie het alle deelnemende lande ‘n paneel sera ontvang met voorafbepaalde waardes wat hulle moes analiseer. Diè waardes was gebruik om verwysingswaardes te herkalibeer asook om waardes van die verskillende lande te kombineer en harmoniseer. Parametiese – asook nie-parametiese statisiek metodes was gebruik om NW te bepaal voor en na latente abnormale waarde uitskakelings (LAVE) toegepas was. Resultate 596 deelenemers het deelgeneem; daar slegs 533 oor na toepassing van streng kriteria waarvan 260 (48.8%) mans en 273 (51.2%) vrouens was. Metaboliese sindroom (MetS) voorkoms onder deelnemers was 25.6%. < 1% van deelnemers het ‘n verminderde geskatte glomulêre filtrasie tempo (eGFR) gehad. Geslag spesifieke NW was nodig vir uriensuur, kreatinien, totale bilirubin (TBil), totale cholesterol (TC), transaminases, transferrien, transferrien saturasie en immunoglobulien – M. Ouderdom spesifieke NW was nodig vir glukose en trigliseriede vir beide geslagte. NW vir vroulike deelnemers vir ureum, magnesium, TC, HDL-cholesterol verhouding, alkaliese phosfatase (ALP) en ferritien. NW vir Kenya kon vergelyk word met ander lande wat deelgeneem het met etlike uitsonderings vir boonste limiet waardes vir TBil en c-reaktiewe protein (CRP). Die NW van Suid Afrika vir uriensuur, lae densiteit lipoprotein cholesterol, alanine transaminase, laktaat dehidrogenase, ALP, albumien, magnesium, tiroïd stumulerings hormoon en prostaat spesifieke antigeen was laer as die NW van Kenya. Konklusie NW vir Keyna was bepaal deur ‘n geharmoniseerde protokol met goed gedefiniheerde verwysingsraamwerk en kan dien as verwysingsraamwerk vir ander laboratoria in die streek asook vir sub-Sahara Afrika lande vir algemene haematologiese – en kliniese chemie toetse. Kenya en RSA se NW’s kon nie geharmoniseer word nie; dit kan lei tot misklassifikasie van pasiente as óf gesond óf met onderliggende siektetoestande.
AFRIKAANS OPSOMMING: Inleiding Laboratorium uitslae speel ‘n belangrike rol in die behandeling en diagnose van onderliggende siektes in pasiente. Normale reikwydtes (NW) vertoon verskillend oor bevolkingsgroepe om verskeie redes: etniese- en verwysings polulasie verskille asook verskillende statistiese metodes wat gebruik word. Die Internationale Federasie van Kliniese Chemie se kommitee vir reikwydtes en bepalings limiete koördineer ‘n globale projek om te bepaal of NW geharmoniseer kan word of nie. Kenya was die enigste land in Oos Afrika wat aan die globale projek deegeneem het. Kenya NW’s kan dien as verwysingsraamwerk vir ander laboratoria in die streek. Dit is belangrik in studies van hierdie aard om te bepaal watter faktore variasies in NW sal veroorsaak en die noodsaklikheid om ‘n skeiding te maak in NW om dit spesifiek te maak vir ouderdom en geslag. Hierdie studie het die NW van Kenya met die van Suid Afrika (RSA) vergelyk wat ook deegeneem het aan die globale projek. Metode Werwing van deelnemers in diè studie was gedoen in verskeie graafskappe in Kenya tussen Januarie en Oktober 2015 met ingeligte toestemming. Gesonde deelnemers was toegelaat om deel te neem tussen 18 – 65 jarige ouderdom, met verdere subverdeel in 4 verskillende ouderdomsgroepe: 18 – 29, 30 – 39, 40 – 49 en 50 – 65. Haematologiese analise van bloedmonsters was gedoen by PathCare Laboratorium in Nairobi, Kenya. Alle ander analise was gedoen was by PathCare se Verwysingslaboratorium in Kaapstad, RSA. Vir die doeleindes van die globale studie het alle deelnemende lande ‘n paneel sera ontvang met voorafbepaalde waardes wat hulle moes analiseer. Diè waardes was gebruik om verwysingswaardes te herkalibeer asook om waardes van die verskillende lande te kombineer en harmoniseer. Parametiese – asook nie-parametiese statisiek metodes was gebruik om NW te bepaal voor en na latente abnormale waarde uitskakelings (LAVE) toegepas was. Resultate 596 deelenemers het deelgeneem; daar slegs 533 oor na toepassing van streng kriteria waarvan 260 (48.8%) mans en 273 (51.2%) vrouens was. Metaboliese sindroom (MetS) voorkoms onder deelnemers was 25.6%. < 1% van deelnemers het ‘n verminderde geskatte glomulêre filtrasie tempo (eGFR) gehad. Geslag spesifieke NW was nodig vir uriensuur, kreatinien, totale bilirubin (TBil), totale cholesterol (TC), transaminases, transferrien, transferrien saturasie en immunoglobulien – M. Ouderdom spesifieke NW was nodig vir glukose en trigliseriede vir beide geslagte. NW vir vroulike deelnemers vir ureum, magnesium, TC, HDL-cholesterol verhouding, alkaliese phosfatase (ALP) en ferritien. NW vir Kenya kon vergelyk word met ander lande wat deelgeneem het met etlike uitsonderings vir boonste limiet waardes vir TBil en c-reaktiewe protein (CRP). Die NW van Suid Afrika vir uriensuur, lae densiteit lipoprotein cholesterol, alanine transaminase, laktaat dehidrogenase, ALP, albumien, magnesium, tiroïd stumulerings hormoon en prostaat spesifieke antigeen was laer as die NW van Kenya. Konklusie NW vir Keyna was bepaal deur ‘n geharmoniseerde protokol met goed gedefiniheerde verwysingsraamwerk en kan dien as verwysingsraamwerk vir ander laboratoria in die streek asook vir sub-Sahara Afrika lande vir algemene haematologiese – en kliniese chemie toetse. Kenya en RSA se NW’s kon nie geharmoniseer word nie; dit kan lei tot misklassifikasie van pasiente as óf gesond óf met onderliggende siektetoestande.
Description
Thesis (PhD)--Stellenbosch University, 2020
Keywords
Reference intervals, Diagnosis, Laboratory, Clinical chemistry, Haematology, UCTD