Skipper Caleb, Tadeo Kiiza, Martyn Emily, Nalintya Elizabeth, Rajasingham Radha, Meya David B, Kafufu Bosco, Rhein Joshua, Boulware David R
Infectious Diseases Institute, Makerere University, Kampala, Uganda
University of Minnesota, Minneapolis, Minnesota, USA.
J Clin Microbiol. 2020 Mar 25;58(4). doi: 10.1128/JCM.02046-19.
Early cryptococcal disease can be detected via circulating antigen in blood before fulminant meningitis develops, when early antifungal therapy improves survival. Two semiquantitative cryptococcal antigen (CrAg) lateral flow assays (LFAs) have been developed, but their diagnostic performance has not been defined. Cryopreserved serum samples from HIV-infected Ugandans obtained as part of a prospective CrAg-screening cohort were tested in duplicate for CrAg by the CrAgSQ (IMMY) and CryptoPS (Biosynex) lateral flow assays. Case-controlled diagnostic performance was measured using the FDA-approved CrAg LFA (IMMY) as a reference standard via McNemar's test. Of 99 serum samples tested, 57 were CrAg positive (CrAg) by the CrAg LFA reference standard. By CrAgSQ, 57 were read as positive, with 98% sensitivity (56/57; 95% confidence interval [CI], 0.91 to 0.99) and 98% specificity (41/42; 95% CI, 0.88 to 0.99) (McNemar's, = 0.99). The sample with a false-negative result by CrAgSQ ( = 1) had a titer of <1:5, while the sample with a false-positive result ( = 1) yielded a 1+ result. By CryptoPS, 52 samples were read as positive, with 88% sensitivity (50/57; 95% CI, 0.76 to 0.95) and 95% specificity (40/42; 95% CI, 0.84 to 0.99) (McNemar's, = 0.18). The CryptoPS false-negative results included samples with titers of <1:5 ( = 1), 1:5 ( = 5), and 1:20 ( = 1), while samples with false-positive results by CryptoPS ( = 2) yielded Positive results. The CryptoPS assay missed 35% (7/20) of samples with CrAg LFA titers of ≤1:20. The new semiquantitative CrAg LFAs allow rapid estimation of titer levels in easy-to-perform platforms. The CrAgSQ demonstrated better qualitative sensitivity and specificity than the CryptoPS compared to the reference standard. The exact grading of the CrAgSQ results has some subjectivity, with interreader variability; however, qualitative reads were generally concordant for both assays.
在暴发性脑膜炎发生之前，早期隐球菌病可通过血液中的循环抗原检测出来，此时早期抗真菌治疗可提高生存率。现已开发出两种半定量隐球菌抗原（CrAg）侧向流动分析法（LFAs），但其诊断性能尚未明确。作为前瞻性CrAg筛查队列的一部分，收集了来自感染HIV的乌干达人的冷冻血清样本，使用CrAgSQ（IMMY）和CryptoPS（Biosynex）侧向流动分析法对CrAg进行重复检测。以FDA批准的CrAg LFA（IMMY）作为参考标准，通过McNemar检验来衡量病例对照诊断性能。在检测的99份血清样本中，根据CrAg LFA参考标准，57份为CrAg阳性（CrAg）。通过CrAgSQ检测，57份样本被判定为阳性，灵敏度为98%（56/57；95%置信区间[CI]，0.91至0.99），特异性为98%（41/42；95%CI，0.88至0.99）（McNemar检验，P = 0.99）。CrAgSQ检测结果为假阴性的样本（P = 1）滴度<1:5，而假阳性样本（P = 1）检测结果为1+。通过CryptoPS检测，52份样本被判定为阳性，灵敏度为88%（50/57；95%CI，0.76至0.95），特异性为95%（40/42；95%CI，0.84至0.99）（McNemar检验，P = 0.18）。CryptoPS的假阴性结果包括滴度<1:5（P = 1）、1:5（P = 5）和1:20（P = 1）的样本，而CryptoPS检测结果为假阳性的样本（P = 2）检测结果为阳性。对于CrAg LFA滴度≤1:20的样本，CryptoPS检测法漏检了35%（7/20）。新型半定量CrAg LFAs能够在易于操作的平台上快速估计滴度水平。与参考标准相比，CrAgSQ在定性灵敏度和特异性方面表现优于CryptoPS。CrAgSQ结果的精确分级存在一定主观性，不同阅片者之间存在差异；然而，两种检测法的定性读数总体上是一致的。
