Kandel et al. (2021) [28] | 28 August 2020–25 September 2020 | Canada | Three outpatient COVID-19 assessment centres | 10.53 | Suspected, symptomatic and asymptomatic outpatients | NA | NPS, 0.9% saline gargle | Swish and gargle three times with 3 mL of 0.9% normal saline | Median: 33 IQR: 24–51 | Yes | E, 5′UTR#, S¶, ORF1ab¶ | 38#, 37¶ | Yes | Moderate |
Dumaresq et al. (2021) [57] | 8 October 2020–23 October 2020 | Canada | Drive-through test centre | 12.04 | Suspected, symptomatic and asymptomatic individuals | NA | Combined ONPS, natural spring water gargle | Rinse the mouth with 5 mL of natural spring water for 5 s, tilt the head back and gargle for 5 s, repeat this cycle once, expel the water back in the plastic cup and empty it in a 15 mL conical polypropylene centrifuge tube | Median: 40 Range: 6–91 | Yes | RdRP, N, E | NA | Yes | High |
Olearo et al. (2021) [49] | 1 December 2020–28 February 2021 | Germany | University hospital | 3.45 | Asymptomatic HCW | NA | NPS, tap water gargle | Gargle at home with 5–7 mL of tap water for 30 s, spit into an empty 10 mL sterile container using a straw, with instructions in flyers and videos | NA | No | ORF1ab, E | NA | Yes | Moderate |
Zander et al. (2021) [54] | October, 2020–December, 2020 | Germany | Doctors' offices | 32.50 | Suspected mostly symptomatic outpatients | NA | NPS, saline gargle | 30 s gargling of 5 mL 0.9% NaCl | Range: 13–89 | Yes | E | 35 | Yes | High |
Kocagoz et al. (2021) [55] | NA | Turkey | Hospital | 20.94 | Suspected symptomatic inpatients | NA | NPS, drinking water gargle | Take a few sips of regular drinking water, gargle and rigorously rinse the mouth forcefully with drinking water for at least 10 s, spit into an empty cup | Range: ≥18 | No | ORF1ab | NA | Yes | Moderate |
Benoit et al. (2021) [50] | November 2020–December 2020 | Canada | Two COVID-19 screening clinics | 20.03 | Suspected, symptomatic outpatients or asymptomatic close contacts | NA | Combined ONPS, natural spring water gargle | Gargle with 5 mL of natural spring water for 5 s in the mouth, 5 s in the throat, to repeat the cycle once, then spit in the initial goblet | NA | NA | ORF1ab, E | NA | Yes | High |
Utama et al. (2022) [59] | 3 March 2021–19 July 2021 | Indonesia | Hospital | 60.66 | Suspected symptomatic and asymptomatic outpatients; confirmed symptomatic and asymptomatic COVID-19 inpatients and SARS-CoV-2-negative inpatients | Previously diagnosed COVID-19-positive and admitted to hospitals+ | Combined ONPS, gargle§ | Satisfy 45-min fasting period, deeply inhale 5–6 times, throat cough 5–6 times, gargle 2.5 mL of gargle solution, spit into a collection tube with 3 mL BioSaliva Collection Buffer, with instructions in the protocol, and supervised by HCW | Mean: 34.3±12.5 (outpatients); 45.4±16.5 (inpatients) | Yes | Helicase, RdRP | 40 | Yes | Moderate |
Goldfarb et al. (2021) [47] | 8 May 2020–11 September 2020 | Canada | COVID-19 collection centre and residence | 74.47 | Confirmed and suspected, symptomatic and asymptomatic COVID-19 outpatients | Had SARS-CoV-2 detected in any clinical sample within a median of 3 days from infection confirmation+ | NPS, sterile 0.9% saline gargle | Swish 5 mL of sterile 0.9% saline in the mouths for 5 s followed by tilting the head back and gargling for 5 s. This gargle cycle was repeated two more times and the saline was expelled into a sterile empty container | Range: 4–71 | Yes | E, RdRp | 40 | Yes | Moderate |
Michel et al. (2021) [36] | May 2020 | Germany | Refugee facility | 51.32 | Confirmed and suspected, asymptomatic individuals | Had a previous positive PCR-test for SARS-CoV-2 at a median time of 14 days prior+ | Combined ONPS, sterile water gargle | Gargling for at least 5 s with 10 mL sterile water under the supervision of medical personnel; gargling was demonstrated if necessary | Mean: 29 Range: 7–59 | Yes | E, ORF1a | 40 | Yes | Moderate |
Guo et al. (2020) [46] | 23 March 2020–31 March 2020 | China | Hospital | 4.17 | Confirmed COVID-19 hospitalised and discharged patients | Laboratory-confirmed COVID-19, met the diagnosis criteria of COVID-19 as per national guideline, within 48–57 days of symptom onset | NPS, sterile normal saline gargle | Oscillate over the posterior pharyngeal wall with 20 mL of sterile normal saline for 5–10 s, then spit out the saline into a sterile container | Range: 26–83 | No | N, ORF1ab | NA | Yes | Moderate |
Poukka et al. (2021) [29] | NA | Finland | Acute COVID-19 outpatients | 95 | Confirmed symptomatic and asymptomatic COVID-19 outpatients | Had been diagnosed with SARS-CoV-2 infection by RT-PCR on NPS within 1–2 days of diagnosis | NPS, water gargle | Gargle sip of water (1/4 of a glass) for 5–20 s before spitting it into a container | Mean: 38.7±12.6 Range: ≥3 | NA | E | NA | Yes | Moderate |
Gertler et al. (2021) [48] | 7 December 2020–11 January 2021 | Germany | University hospital and residence | 100 | Confirmed symptomatic COVID-19 outpatients | Initial laboratory RT-PCR confirmation of SARS-CoV-2 by professional-collected, combined ONPS in a testing centre, enrolled within 2–15 days from symptom onset | Combined ONPS, tap water gargle | Gargle 10 mL tap water and spit into a plastic container; written instructions and observed without any additional verbal instructions | Median: 31.5 Range: 17–66 | Yes | E, ORF1ab | NA | Yes | Moderate |
Mittal et al. (2020) [35] | May 2020–June 2020 | India | Tertiary care hospital | 100 | Confirmed symptomatic and asymptomatic COVID-19 inpatients | RT-PCR-confirmed patients with SARS-CoV-2 infection within 72 h of diagnosis by a trained HCW, as per the national and hospital policies | NPS, sterile normal saline gargle | Perform gargle with 8–10 mL sterile normal saline for 15–20 s and spit back to a screw-capped container | Mean: 45.08±12.78 | No | N1, N2 | 40 | Yes | Moderate |
Kwon et al. (2022) [58] | 7 May 2021–7 July 2021 | Korea | Medical centres and hospital | 50.50 | Confirmed symptomatic and asymptomatic COVID-19 inpatients and healthy individuals | Previously confirmed COVID-19 patients hospitalised in medical centres and hospital+ | NPS, Bean extract gargle | Swirl and gargle 5 mL of bean extract-based gargle for 2 min, spit into a tube | Mean: 43.7, Range: 18–83 | No | RdRP, E, N | NA | Yes | Moderate |
Hitzenbichler et al. (2021) [51] | 27 April 2020–8 December 2020 | Germany | Medical centre | 85.29 | Confirmed symptomatic and asymptomatic COVID-19 inpatients | Patients with COVID-19 admitted to nonintensive care medical ward, with laboratory-confirmed SARS-CoV-2 infection (defined by a positive RT-qPCR result before inclusion) | NPS, sterile saline or water gargle | Gargle 10 mL medical grade saline or water for 5–10 s, oscillating over the posterior pharyngeal wall, transfer the liquid into a sterile test tube | Mean: 57.5±14.9, Range: 22–83 | No | E | NA | Yes | Moderate |
Kinshella et al. (2021) [52] | 4 September 2020–29 October 2020 | Canada | Hospital COVID-19 collection centre | 100 | Confirmed symptomatic COVID-19 outpatients | Patients with positive RT-PCR result of NPS | NPS, sterile saline gargle | Swish 5 mL of sterile 0.9% saline for 5 s, tilt the head back and gargle for 5 s. Repeat the swish and gargle cycle two more times, expel the saline into a sterile empty container. Saline gargle was self-collected with collection observed by nursing staff, or with written and visual collection instructions, but no observation and no guidance provided by an HCW | Median: 29.5 IQR: 14–41 | Yes | E, RdRP | 40 | Yes | Moderate |
Biber et al. (2021) [53] | July 2020–September 2020 | Israel | Nonhospital facilities dedicated to COVID-19 patients in isolation | 84.67 | Confirmed symptomatic and asymptomatic COVID-19 outpatients in isolation | COVID-19 outpatients previously RT-PCR-confirmed by combined ONPS | Combined ONPS, normal saline (0.9%) gargle | Rinse and gargle 10 cc (10 mL) of normal saline (0.9%) for 10–20 s, spit into a sterile container | Range: 18–73 | No | N, E, RdRP | 40 | Yes | High |
Casati et al. (2022) [56] | NA | Germany | Medical university | 48.72 | Confirmed symptomatic COVID-19 ambulatory patients and negative close contacts | Previously tested positive for SARS-CoV-2 via RT-PCR on NPS+ | NPS, sterile saline gargle | Perform gargling with 8 mL of sterile 0.9% saline, and spit into a sterile container without additives, after verbal and visual instructions | NA | NA | E | NA | Yes | Moderate |