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Reference intervals for serum cystatin C and creatinine of an indigenous adult Nigerian population.

BACKGROUND AND AIM
Estimation of the glomerular filtration rate (GFR) is important for the evaluation of patients with kidney disease. Some studies suggest that GFR estimated from serum cystatin C (Cys C) is more accurate than that from serum creatinine (SCr). For Cys C to be used for this purpose, normal values need to be determined for various populations. This study determined the serum Cys C levels and reference intervals (RIs) of a Nigerian population.


MATERIALS AND METHODS
Three hundred and four healthy adult subjects were analysed. Serum Cys C and SCr were determined by particle enhanced turbidimetric immunoassay and modified Jaffe kinetic method respectively. Data were analysed using the Statistical Package for Social Sciences version 17.0 (SPSS for Windows Inc., Chicago, IL, USA). Estimation of RIs was done as per the International Federation of Clinical Chemistry guidelines.


RESULTS
The RIs for Cys C were 0.65-1.12 mg/L (median 0.86) for males, 0.62-1.12 mg/L (median 0.85) for females and 0.64-1.12 mg/L (median 0.86) for all the subjects. The RIs for SCr were 73-110 μmol/L (median 89) for males, 65-102 μmol/L (median 82) for females and 66-106 μmol/L (median 86) for all the subjects. There was no significant gender difference in the RIs for serum Cys C, (P > 0.05). The SCr levels and RI were significantly lower in females than in males (P < 0.001).


CONCLUSION
This study has determined the serum Cys C levels and RI of an indigenous healthy adult black population in Nigeria.