Kumarasamy N, Mahajan Anish P, Flanigan Timothy P, Hemalatha R, Mayer Kenneth H, Carpenter Charles C J, Thyagarajan S P, Solomon Suniti
Y.R.G. Centre for AIDS Research and Education, Chennai, India.
J Acquir Immune Defic Syndr. 2002 Dec 1;31(4):378-83. doi: 10.1097/00126334-200212010-00002.
In most resource-constrained countries, CD4 cell count testing is prohibitively expensive for routine clinical use and is not widely available. As a result, physicians are often required to make decisions about opportunistic infection (OI) chemoprophylaxis without a laboratory evaluation of HIV stage and level of immunosuppression. OBJECTIVES To evaluate the correlation of total lymphocyte count (TLC), an inexpensive and widely available parameter, to CD4 count. To determine a range of TLC cutoffs for the initiation of OI prophylaxis that is appropriate for resource-constrained settings.
Spearman correlation between CD4 count and TLC was assessed in patients attending an HIV/AIDS clinic in South India. Positive predictive value (PPV), negative predictive value (NPV), and sensitivity and specificity of various TLC cutoffs were computed for CD4 count <200 cells/mm3 and <350 cells/mm3. Correlation and statistical indices computed for all patients and for patients dually infected with HIV and active tuberculosis.
High degree of correlation was noted between 650 paired CD4 and TLC counts (r = 0.744). TLC <1400 cells/mm3 had a 76% PPV, 86% NPV, and was 73% sensitive, 88% specific for CD4 count <200 cells/mm3. TLC <1700 cells/mm3 had a 86% PPV, 69% NPV, and was 70% sensitive, 86% specific for CD4 count <350 cells/mm3. The cost of a single CD4 count in India is approximately 30 US dollars, whereas the cost of a single TLC is 0.80 US dollars.
TLC could serve as a low-cost tool for determining both a patient's risk of OI and when to initiate prophylaxis in resource-constrained settings. PPV, NPV, sensitivity, and specificity maximally aggregated at TLC <1400 cells/mm3 for CD4 <200 cell/mm3 and TLC <1700 cells/mm3 for CD4 <350 cells/mm3. Selection of appropriate TLC cutoffs for prophylaxis administration should be made on a regional basis depending on OI incidence, antimicrobial resistance patterns, and availability of the antimicrobials.
在大多数资源有限的国家，用于常规临床检测的CD4细胞计数成本过高，难以广泛应用。因此，医生在没有对HIV疾病阶段和免疫抑制水平进行实验室评估的情况下，常常需要就机会性感染（OI）化学预防做出决策。目的评估总淋巴细胞计数（TLC）这一廉价且广泛可用的参数与CD4计数之间的相关性。确定在资源有限的环境中启动OI预防的TLC临界值范围。
在印度南部一家HIV/AIDS诊所就诊的患者中评估CD4计数与TLC之间的Spearman相关性。计算CD4计数<200个细胞/mm³和<350个细胞/mm³时，各种TLC临界值的阳性预测值（PPV）、阴性预测值（NPV）、敏感性和特异性。计算所有患者以及同时感染HIV和活动性结核病患者的相关性和统计指标。
650对CD4和TLC计数之间存在高度相关性（r = 0.744）。TLC<1400个细胞/mm³时，PPV为76%，NPV为86%，对于CD4计数<200个细胞/mm³的敏感性为73%，特异性为88%。TLC<1700个细胞/mm³时，PPV为86%，NPV为69%，对于CD4计数<350个细胞/mm³的敏感性为70%，特异性为86%。在印度，单次CD4计数的成本约为30美元，而单次TLC的成本为0.80美元。
在资源有限的环境中，TLC可作为一种低成本工具，用于确定患者发生OI的风险以及何时开始预防。对于CD4<200个细胞/mm³，PPV、NPV、敏感性和特异性在TLC<1400个细胞/mm³时达到最大值；对于CD4<350个细胞/mm³，在TLC<1700个细胞/mm³时达到最大值。应根据OI发病率、抗菌药物耐药模式以及抗菌药物的可获得性，在区域基础上选择用于预防给药的合适TLC临界值。
