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Observational Study
. 2021 May;8(1):e000590.
doi: 10.1136/bmjgast-2020-000590.

The value of anal swab RT-PCR for COVID-19 diagnosis in adult Indonesian patients

Murdani Abdullah  1   2 , Dedy Gunawanjati Sudrajat  1 , Virly Nanda Muzellina  3 , Juferdy Kurniawan  4 , Aulia Rizka  5 , Amanda Pitarini Utari  1 , Rabbinu Rangga Pribadi  1 , Muhammad Firhat Idrus  1 , Yusra Yusra  6 , Sofy Meilany  7 , Andry Surandy  1 , Hamzah Shatri  8 , Ikhwan Rinaldi  9 , Ceva Wicaksono Pitoyo  10 , Kaka Renaldi  1
Affiliations
Observational Study

The value of anal swab RT-PCR for COVID-19 diagnosis in adult Indonesian patients

Murdani Abdullah et al. BMJ Open Gastroenterol. 2021 May.

Abstract

Objective: This study will test the performance of the anal swab PCR test when compared with the nasopharyngeal swab PCR test as a diagnostic tool for COVID-19.

Design: An observational descriptive study which included hospitalised suspected, or probable cases of hopitalised COVID-19 patients, conducted in Dr. Cipto Mangunkusumo National Hospital, Ciputra Hospital, Mitra Keluarga Depok Hospital and Mitra Keluarga Kelapa Gading Hospital, Indonesia. Epidemiological, clinical, laboratory and radiology data were obtained. Nasopharyngeal and anal swabs specimens were collected for SARS-CoV-2 RNA detection.

Results: We analysed 136 subjects as part of this study. The clinical spectrum of COVID-19 manifesation in this study was typical of hospitalised patients, with 25% classified as mild cases, 14.7% in severe condition and 12.5% of subjects classified as having acute respiratory distress syndrome. When compared with nasopharyngeal swab as the standard specimen for reverse transcription polymerase chain reaction (RT-PCR) detection of SARS-CoV-2 antigen, the sensitivity and specificity of the anal swab was 36.7% and 93.8%, respectively. The positive and negative predictive value were 97.8% and 16.5 %, respectively. The performance of the anal swab remained similar when only the subgroup of patients with gastrointestinal symptoms (n=92, 67.6%) was analysed (sensitivity 40% and specificity 91.7%). Out of all the subjects included in analysis, 67.6% had gastrointestinal symptoms. Similarly, 73.3% of patients in the anal swab-positive group had gastrointestinal symptoms. The two most common gastrointestinal symptoms in the subjects' population were nausea and anorexia.

Conclusion: Anal swab specimen has low sensitivity (36.7%) but high specificity (93.8%) for detecting SARS-CoV-2 antigen by RT-PCR. Only one additional positive result was found by anal swab among the nasopharyngeal swab-negative group. Anal swab may not be needed as an additional test at the beginning of a patient's diagnostic investigation and nasopharyngeal swab RT-PCR remains as the standard diagnostic test for COVID-19.

Keywords: COVID-19; anal; diagnostic virology.

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Conflict of interest statement

Competing interests: MA reports grants from Indonesian Ministry of Research, Technology and Higher Education during the conduct of the study. DGS has nothing to disclose. VNM has nothing to disclose. JK has nothing to disclose. AR has nothing to disclose. APU has nothing to disclose. RRP has nothing to disclose. MFI has nothing to disclose. YY has nothing to disclose. SM has nothing to disclose. AS has nothing to disclose. HS has nothing to disclose. IR has nothing to disclose. CWP has nothing to disclose. KR has nothing to disclose.

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