Department of Medicine, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India.
Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India.
PLoS One. 2020 Dec 31;15(12):e0244870. doi: 10.1371/journal.pone.0244870. eCollection 2020.
Previous studies on diagnostic accuracy of dipstick testing for leukocyte esterase (LE) and nitrite to diagnose urinary tract infection (UTI) had used urine culture, which is an imperfect gold standard. Estimates of diagnostic accuracy obtained using the classical gold standard framework might not reflect the true diagnostic accuracy of dipstick tests.
We used the dataset from a prospective, observational study conducted in the emergency department of a teaching hospital in southern India. Patients with a clinical suspicion of UTI underwent dipstick testing for LE and nitrite, urine microscopy, and urine culture. Based on the results of urine microscopy and culture, UTI was classified into definite, probable, and possible. Patients with microscopic pyuria and a positive urine culture were adjudicated as definite UTI. Unequivocal imaging evidence of emphysematous pyelonephritis or perinephric collections was also considered definite UTI. We estimated the diagnostic accuracy of LE and nitrite tests using the classical analysis (assuming definite UTI as gold standard) and two different Bayesian latent class models (LCMs; 3-tests in 1-population and 2-tests in 2-populations models).
We studied 149 patients. Overall, 64 (43%) patients had definite, 76 (51%) had probable, and 2 (1.3%) had possible UTI; 7 (4.6%) had alternate diagnoses. In classical analysis, LE was more sensitive than nitrite (87.5% versus 70.5%), while nitrite was more specific (24% versus 58%). The 3-tests in 1-population Bayesian LCM indicated a substantially better sensitivity and specificity for LE (98.1% and 47.6%) and nitrite (88.2% and 97.7%). True sensitivity and specificity of urine culture as estimated by the model was 48.7% and 73.0%. Estimates of the 2-tests in 2-populations model were in agreement with the 3-tests in 1-population model.
Bayesian LCMs indicate a clinically important improvement in the true diagnostic accuracy of urine dipstick testing for LE and nitrite. Given this, a negative dipstick LE would rule-out UTI, while a positive dipstick nitrite would rule-in UTI in our study setting. True diagnostic accuracy of urine dipstick testing for UTI in various practice settings needs reevaluation using Bayesian LCMs.
先前关于白细胞酯酶（LE）和亚硝酸盐检测用于诊断尿路感染（UTI）的诊断准确性的研究使用了尿液培养，这是一种不完美的金标准。使用经典金标准框架获得的诊断准确性估计可能无法反映尿液试纸检测的真实诊断准确性。
我们使用了在印度南部一所教学医院急诊科进行的前瞻性观察研究的数据。临床怀疑患有 UTI 的患者接受 LE 和亚硝酸盐尿液试纸检测、尿液显微镜检查和尿液培养。根据尿液显微镜检查和培养的结果，将 UTI 分为明确型、可能型和疑似型。有显微镜下脓尿和阳性尿液培养的患者被判定为明确型 UTI。有明确的影像学证据表明气肿性肾盂肾炎或肾周脓肿也被认为是明确型 UTI。我们使用经典分析（将明确型 UTI 作为金标准）和两种不同的贝叶斯潜在类别模型（LCM；单总体 3 检验和双总体 2 检验模型）来估计 LE 和亚硝酸盐检测的诊断准确性。
我们研究了 149 名患者。总体而言，64 名（43%）患者为明确型，76 名（51%）为可能型，2 名（1.3%）为疑似型；7 名（4.6%）为其他诊断。在经典分析中，LE 的敏感性高于亚硝酸盐（87.5%比 70.5%），而亚硝酸盐的特异性更高（24%比 58%）。单总体 3 检验贝叶斯 LCM 表明 LE（98.1%和 47.6%）和亚硝酸盐（88.2%和 97.7%）的敏感性和特异性有显著提高。模型估计的尿液培养的真实敏感性和特异性分别为 48.7%和 73.0%。双总体 2 检验模型的估计结果与单总体 3 检验模型一致。
贝叶斯 LCM 表明 LE 和亚硝酸盐尿液试纸检测的真实诊断准确性有了显著提高。根据这一结果，LE 阴性尿液试纸可排除 UTI，而阳性尿液试纸可提示 UTI，这在我们的研究环境中是成立的。在各种实际环境中，需要使用贝叶斯 LCM 重新评估尿液试纸检测 UTI 的诊断准确性。
