Jose Arun, Medhi Priyanka, Varkki Sneha Deena, Loganathan Thondaiman, Christudoss Pamela, Karuppusami Reka
Department of Clinical Biochemistry, Christian Medical College, Vellore, India.
Department of Child Health, Christian Medical College, Vellore, India.
Indian J Med Res. 2025 Mar;161(3):207-214. doi: 10.25259/IJMR_1754_2024.
Background & objectives Availability of sweat chloride analysis, the gold standard test for diagnosis of Cystic Fibrosis (CF) faces significant challenges in India. This study aimed to compare sweat conductivity using Sweat-Chek™ Sweat Analyzer against sweat chloride analysis using the 926 Sherwood chloride analyser and assess if sweat conductivity test can guide CF diagnosis in resource-poor settings. Methods In this retrospective study sweat chloride analysis and sweat conductivity were simultaneously performed on samples collected via Macroduct® system from patients referred for sweat testing. CF diagnosis was based on sweat chloride levels: ≥60 mmol/l confirmed CF, 30-59 mmol/l was borderline, and <30 mmol/l excluded CF. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV), and area under curve (AUC) were calculated via ROC curve. Spearman's rho was employed to analyse the correlation between methods. Results Both tests were performed on 118 children of which 106 samples were adequately collected. CF was diagnosed in 11 children. Sweat conductivity ≥ 80 mmol/l diagnosed CF with 100 per cent sensitivity, specificity, PPV, and NPV. Likewise, a value ≤ 49 mmol/l predicted absence of CF with 100 per cent sensitivity, 91.36 per cent specificity, 78.13 per cent PPV, and 100 per cent NPV. Spearman's rho of 0.93 (P< 0.001) showed a strong correlation between the two methods. Intermediate conductivity values also correlated well (rs 0.62, P< 0.003) with intermediate sweat chloride levels. Interpretations & conclusions Sweat conductivity reliably identified CF in the study population including those children with borderline levels, suggesting the possibility of its use in resource-limited settings where sweat chloride analyzers are unavailable.
在印度，作为囊性纤维化（CF）诊断金标准的汗液氯化物分析面临重大挑战。本研究旨在使用Sweat-Chek™汗液分析仪比较汗液电导率与使用926 Sherwood氯化物分析仪进行的汗液氯化物分析，并评估汗液电导率测试能否在资源匮乏地区指导CF诊断。方法：在这项回顾性研究中，对通过Macroduct®系统从转诊进行汗液测试的患者收集的样本同时进行汗液氯化物分析和汗液电导率检测。CF诊断基于汗液氯化物水平：≥60 mmol/l确诊为CF，30 - 59 mmol/l为临界值，<30 mmol/l排除CF。通过ROC曲线计算敏感性、特异性、阳性预测值（PPV）、阴性预测值（NPV）和曲线下面积（AUC）。采用Spearman秩相关系数分析两种方法之间的相关性。结果：对118名儿童进行了两项测试，其中106个样本采集充分。11名儿童被诊断为CF。汗液电导率≥80 mmol/l诊断CF时，敏感性、特异性、PPV和NPV均为100%。同样，≤49 mmol/l的值预测无CF时，敏感性为100%，特异性为91.36%，PPV为78.13%，NPV为100%。Spearman秩相关系数为0.93（P<0.001），表明两种方法之间存在强相关性。中等电导率值与中等汗液氯化物水平也具有良好的相关性（rs = 0.62，P<0.003）。解释与结论：在本研究人群中，包括那些临界水平的儿童，汗液电导率能够可靠地识别CF，这表明在没有汗液氯化物分析仪的资源有限地区使用汗液电导率测试的可能性。
