Development of an algorithm of haematologic parameters as surrogate markers for CD4 cell count in resource-limited settings

Abstract

Total Lymphocyte Count (TLC) has been previously evaluated as a surrogate for CD4 counts in the management of HIV especially in resource-limited settings with varying results. This study developed a clinical algorithm of TLC and other significant haematologic parameters to raise the predictive value of TLC in classifying subjects with CD4 count <350 cells/mm 3 . Total samples of 215 HIV-seropositive ARVnaïve patients were studied. The Beckman Counter was used for Complete Blood count (CBC), Beckton Dickinson FACS count for CD4 count, and Westergren method for Erythrocyte Sedimentation Rate (ESR). The variables retained as the most significant predictors (at p<0.05) were TLC<2000 cells/mm 3 (sensitivity 71.5%, specificity 73.4%, PPV 69.1%, NPV 78.3%), Hb < 12 g/dl (sensitivity 59.8%, specificity 56.2%, PPV 63.3%, NPV 71%) and ESR>30 mm/h(sensitivity 57%, specificity 71%, PPV 66%, NPV 68%). A three-step algorithm of TLC <2000 cells/mm 3 , Hb<12 g/dl, and ESR>30 mm/h for predicting CD4 count<350 cells/mm 3 yielded sensitivity 66%, specificity 82%, PPV 72%, NPV 77% (area under curve AUC 0.79). This algorithm had a higher predictive accuracy making it a better tool than the use of TLC alone in monitoring disease progression in resource-limited settings.