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Covert COVID-19 and false-positive dengue serology in Singapore

2020; Elsevier BV; Volume: 20; Issue: 5 Linguagem: Inglês

10.1016/s1473-3099(20)30158-4

1474-4457

Gabriel Yan, Chun Kiat Lee, Lawrence Lam, Benedict Yan, Ying Xian Chua, Anita Y. N. Lim, Kee Fong Phang, Guan Sen Kew, Hazel Teng, Chin Hong Ngai, Li Lin, Rui Min Foo, Surinder Pada, Lee Ching Ng, Paul Anantharajah Tambyah,

COVID-19 epidemiological studies

Dengue and coronavirus disease 2019 (COVID-19) are difficult to distinguish because they have shared clinical and laboratory features.1Chen N Zhou M Dong X et al.Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study.Lancet. 2020; 395: 507-513Summary Full Text Full Text PDF PubMed Scopus (14440) Google Scholar, 2Yan G Pang L Cook AR et al.Distinguishing Zika and dengue viruses through simple clinical assessment, Singapore.Emerg Infect Dis. 2018; 24: 1565-1568Crossref PubMed Scopus (27) Google Scholar We describe two patients in Singapore with false-positive results from rapid serological testing for dengue, who were later confirmed to have severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the causative virus of COVID-19. The first case is a 57-year-old man with no relevant past medical, travel, or contact history, who presented to a regional hospital on Feb 9, 2020, with 3 days of fever and cough. He had thrombocytopenia (platelet count 140 × 109/mL) and a normal chest radiograph. He was discharged after a negative rapid test for dengue NS1, IgM, and IgG (SD Bioline Dengue Duo Kit; Abbott, South Korea). He returned to a public primary health-care clinic with persistent fever, worsening thrombocytopenia (89 × 109/mL), and new onset lymphopenia (0·43 × 109/mL). A repeat dengue rapid test was positive for dengue IgM and IgG (Dengue Combo; Wells Bio, South Korea). He was referred to hospital for dengue with worsening cough and dyspnoea. A chest radiograph led to testing for SARS-CoV-2 by RT-PCR (in-house laboratory-developed test detecting the N and ORF1ab genes) from a nasopharyngeal swab, which returned positive. The original seropositive sample and additional urine and blood samples tested negative for dengue, chikungunya, and Zika viruses by RT-PCR,3Lanciotti RS Calisher CH Gubler DJ Chang GJ Vorndam AV Rapid detection and typing of dengue viruses from clinical samples by using reverse transcriptase-polymerase chain reaction.J Clin Microbiol. 1992; 30: 545-551Crossref PubMed Google Scholar, 4Lanciotti RS Kosoy OL Laven JJ Velez JO Lambert AJ Johnson AJ et al.Genetic and serologic properties of Zika virus associated with an epidemic, Yap State, Micronesia, 2007.Emerg Infect Dis. 2008; 14: 1232-1239Crossref PubMed Scopus (1712) Google Scholar, 5Lim CK Nishibori T Watanabe K Ito M Kotaki A Tanaka K Chikungunya virus isolated from a returnee to Japan from Sri Lanka: isolation of two sub-strains with different characteristics.Am J Trop Med Hyg. 2009; 81: 865-868Crossref PubMed Scopus (34) Google Scholar and a repeat dengue rapid test (SD Bioline) was also negative. Thus, the initial dengue seroconversion result was deemed a false positive. The second case is a 57-year-old woman with no relevant past medical, travel, or contact history, who presented to a regional hospital on Feb 13, 2020, with fever, myalgia, a mild cough of 4 days, and 2 days of diarrhoea. She had thrombocytopenia (92 × 109/mL) and tested positive for dengue IgM (SD Bioline). She was discharged with outpatient follow up for dengue fever. She returned 2 days later with a persistent fever, worsening thrombocytopenia (65 × 109/mL), and new onset lymphopenia (0·94 × 109/mL). Liver function tests were abnormal (aspartate aminotransferase 69 U/L [reference range 10–30 U/L], alanine aminotransferase 67 U/L [reference range <55 U/L], total bilirubin 35·8 μmol/L [reference range 4·7–23·2 μmol/L]). Chest radiography was normal and she was admitted for dengue fever. She remained febrile despite normalisation of her blood counts and developed dyspnoea 3 days after admission. She was found to be positive for SARS-CoV-2 by RT-PCR from a nasopharyngeal swab. A repeat dengue test (SD Bioline) was negative and an earlier blood sample also tested negative for dengue by RT-PCR.6Lura T Su T Brown MQ Preliminary evaluation of Thermo Fisher TaqMan Triplex q-PCR kit for simultaneous detection of chikungunya, dengue, and Zika viruses in mosquitoes.J Vector Ecol. 2019; 44: 205-209Crossref PubMed Scopus (4) Google Scholar The initial dengue IgM result was deemed to be a false positive. Failing to consider COVID-19 because of a positive dengue rapid test result has serious implications not only for the patient but also for public health. Our cases highlight the importance of recognising false-positive dengue serology results (with different commercially available assays) in patients with COVID-19. We emphasise the urgent need for rapid, sensitive, and accessible diagnostic tests for SARS-CoV-2, which need to be highly accurate to protect public health. We declare no competing interests.