Title: Evaluating the Performance of the DPP® ZDC IgM/IgG Rapid Test for Chikungunya Virus Diagnosis in Febrile Outpatients: A Prospective, Diagnostic Accuracy Study Running title: Accuracy of an antibody-based rapid diagnostic test for Chikungunya in Rio Author’ names:

Objective: Evaluate the performance of a novel antibody-based rapid diagnostic test (RDT) for detecting Chikungunya virus (CHIKV) infection in febrile patients in Rio de Janeiro, Brazil. Methods: We prospectively enrolled non-severe febrile patients aged 2-65 years presenting as outpatients between October 2018 and July 2019. Serum samples were collected during acute and convalescent phases and tested for CHIKV antibodies using the DPP® ZDC IgM/IgG rapid test and compared against the reference test, CHIKV RT-PCR. We determined the seropositivity using ELISA IgM/IgG and evaluated the diagnostic performance of the WHO-endorsed CHIKV clinical definition against the reference test. Results: Of 500 participants, 226/261 (86.5%) tested ELISA IgM positive, 45/271 (16.6%) tested ELISA IgG positive, 100/294 (34%) CHIKV RT-PCR positive, and 117/495 (23.6%) RDT-antibody positive. During the acute phase [median 3 (2-4) days post illness onset], the sensitivity of IgM, IgG, and combined IgM/IgG ranged from 14.71-34.85%, while specificity ranged from 63.32-65.61%. During the convalescent phase [mean 16.5 (±5.5) days post-illness onset], sensitivity increased from 65.75% to 77.78%, and specificity ranged from 93.33-98.11%. The WHO's CHIKV clinical definition had a sensitivity, specificity, positive predictive value, and negative predictive value of 88 (79.993.6)%, 74 (68-80)%, 64.2 (58.2-69.8)%, and 92.3 (87.6-95.3)%, respectively. Conclusions: The DPP® ZDC IgM/IgG accurately diagnosed CHIKV on samples collected during the convalescent phase. Field applications include investigating CHIKV in patients with sub-acute to chronic osteoarticular symptoms and conducting serosurveys to inform priority areas for CHIKV vaccine implementation. The WHO's clinical definition of CHIKV was accurate and could be deployed, especially in regions with limited diagnostic capacity. Clinicaltrials.gov: NCT03047642

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