The clinical utility of cystatin c in assessing renal function among HIV/AIDS patients on ART at Mildmay Uganda

Abstract

Background: The risk of death form renal disease among HIV positive individuals can be reduced by early detection and appropriate monitoring. Measurement of glomerular filtration rates is the gold standard assessing renal function. Extra renal factors affecting creatinine concentration, the most widely used molecule in GFR estimation limit its efficiency. Routine use of exogenous substances e.g. inulin to measure GFR is not possible due to cost and complexity. Cystatin C has been proposed as a potential renal function marker but its use in HIV&AIDS patients has not been well evaluated Objective: To assess the clinical utility of Cystatin C based prediction equations in determining renal function among HIV/AIDS infected individuals Methods: A cross sectional study was carried out on 914 HIV&AIDS patients on ART attending Mildmay Uganda for care and treatment between Jan 2015 to March 2015. Serum Cystatin C was measured by a quantitative sandwich enzyme immunoassay using the particle enhanced immunoturbidimetric assay. Creatinine was analyzed using enzymatic Creatinine PAP method. Using the results of the eGFR by creatinine as reference method, the sensitivity, specificity and positive/negative predictive values and likelihood ratios of Cystatin C were calculated. Results: The sensitivity of Cystatin C was 15.1% (95% CI= 8.4, 24) with specificity 99.3% (95% CI=98- 99.7). The positive and negative predictive values were 70.0% (45.7-88.1) and 91.2% (98.11-92.94) respectively. The positive likelihood ratio was 18.81 and negative likelihood ratio was 0.85. Cystatin C had accuracy 90.7 and area under curve 0.768. The prevalence of chronic kidney disease was 10.18%. Conclusion; Cystatin C exhibited a high specificity and a high positive likelihood ratio in diagnosis of kidney disease among HIV&AIDS patients.