False-Negative Serum Cryptococcal Antigen Lateral Flow Immunoassay Result for a Patient with Disseminated Cryptococcal Disease

Abstract

Yuqiao Xu,1,2 Wenying Xia,1,2 Fang Ni1,2 1Department of Laboratory Medicine, Jiangsu Province Hospital and Nanjing Medical University First Affiliated Hospital, Nanjing, People’s Republic of China; 2National Key Clinical Department of Laboratory Medicine, Nanjing, People’s Republic of ChinaCorrespondence: Wenying Xia; Fang NiDepartment of Laboratory Medicine, Jiangsu Province Hospital and Nanjing Medical University First Affiliated Hospital, Guangzhou Street No. 300, 210029, People’s Republic of ChinaTel + 86 25-6830-6287Fax + 86 25- 8372-4440Email [email protected]; [email protected]: Cryptococcus neoformans (C. neoformans) is an opportunistic fungal pathogen to humans, which can be acquired from environmental sources. Its most important virulence factor is its polysaccharide capsule, which can be used for diagnostic tests that identify the cryptococcal antigen (CrAg). The CrAg lateral flow assay (LFA) is a dipstick immunochromatographic assay with high sensitivity and specificity; however, several false-negative cases have been reported. Here, we present a case of a false-negative serum CrAg LFA, in which the blood culture from a matched sample was positive for C. neoformans, thus demonstrating the postzone phenomenon.Keywords: Cryptococcus neoformans, lateral flow immunoassay, postzone phenomenon

Keywords

• cryptococcus neoformans
• lateral flow immunoassay
• postzone phenomenon