Clinical application and evaluation oftwo different methods for detection of cryptococcal capsular polysaccharide antigen in diagnosis and treatment of pulmonary cryptococcosis

Abstract

Abstract:

Objective To evaluate lateral flow assay (LFA) and enzyme-linked immunesorbent assay (ELISA) for detection of cryptococcal capsular polysaccharide antigen (CrAg) in diagnosis and treatment of pulmonary cryptococcosis (PC). Method One hundred and nine cases of suspected PC were collected from January 2016 to June 2018 at Fuzhou Pulmonary Hospital of Fujian.Serum CrAg was detected by ELISA and LFA at the same time, and the diagnostic efficiency of the two methods for PC was compared and analyzed. Serum CrAg concentration was also monitored by ELISA during the treatment. Results Among the 109 patients, 53 cases were confirmed as PC by lung biopsy or cryptococcus detection of lung puncture liquid,56 cases were other lung diseases (Non-PC). The results were as follows:(1) The serum CrAg concentration detected by ELISA in the PC group was[11.43 (5.92, 47.96)] μg/L. The number of cases with serum CrAg ≤ 3.2 μg/L in the PC group was significantly lower than that in the non-PC group (P<0.05), while the number of cases with serum CrAg>5.0 μg/L was significantly higher than that in the non-PC group (P<0.05). The positive rate of serum CrAg detected by LFA in the PC group was significantly higher than that in the non-PC group, and the difference was statistically significant (P<0.05). (2) Receiver Operating Characteristic (ROC) curve analysis showed that the area under the curve of serum CrAg detected by ELISA was 0.939 (95% confidence interval was 0.892~0.985), and 3.54 μg/L was considered as the best cut-off value with the highest Youden index. The sensitivity, specificity, positive predictive value and negative predictive value were 94.3%, 80.4%, 82.0% and 93.8%, respectively. When 5.0 μg/L was taken as the diagnostic cut-off value of serum CrAg, there was no statistical difference in the diagnostic sensitivity between ELISA and LFA (88.7% vs 83.0%, P>0.05), but the specificity of ELISA test (82.1%) was significantly lower than that of LFA test (98.2%), and the difference was statistically significant (P<0.05). The diagnostic sensitivity and specificity of ELISA and LFA were similar (P>0.05) when the cut-off values of serum CrAg were 5.0μg/L, 6.0μg/L and 7.0 μg/L, respectively. The diagnostic sensitivity (62.3%) of ELISA was significantly lower than that of LFA (83.0%) when 8.0 μg/L was taken as the cut-off value of serum CrAg (P<0.05), but the specificity (100% and 98.2%) in the two methods was the same (P>0.05). (4) The serum CrAg concentration was continually monitored in 14 patients during the antifungal therapy. After six months of treatment, the serum CrAg was significantly decreased[19.33 (7.11, 43.46) vs 8.09 (5.39, 11.90) μg/L, P<0.05]. Conclusions 3.54 μg/L was considered as the best diagnostic cut-off value of serum CrAg of ELISA test. However, when 5.0 μg/L was taken as the diagnostic cut-off value, ELISA had good diagnostic sensitivity and specificity similarly to those of LFA, and the two methods had the same diagnostic efficiency. ELISA and LFA were both helpful to the rapid diagnosis of PC and worthy of being widely applied in clinic. Compared with LFA qualitative detection, ELISA could dynamically monitor the changes of serum CrAg concentration, which was useful for the treatment response and prognosis evaluation of PC.

Key words: lateral flow assay, enzyme-linked immunosorbent assay, cryptococcal capsular polysaccharide antigen, pulmonary cryptococcosis

CLC Number:

R379.5

HUANG Jin-bao, LI Hong-yan, LAN Chang-qing, LV Xiao, LIN Zhi-lai, WANG Xin-hang, ZHANG Hong-ying, ZOU Sheng-hua, WEN Heng. Clinical application and evaluation oftwo different methods for detection of cryptococcal capsular polysaccharide antigen in diagnosis and treatment of pulmonary cryptococcosis[J]. Chinese Journal of Mycology, 2019, 14(5): 264-269.

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