TABLE 2

Stratified pooled estimates on diagnostic indicators for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using gargling as an alternative sampling approach among all populations by study characteristics

Study characteristicStudies, nSensitivity estimate (95% CI)I2 (95% CI), %Studies, nSpecificity estimate (95% CI)I2 (95% CI), %PPV estimate (95% CI)I2 (95% CI), %NPV estimate (95% CI)I2 (95% CI), %
Gargle1991 (85–96)88 (86–91)1697 (92–100)96 (95–96)95 (89–99)89 (87–91)91 (81–98)98 (97–98)
Population
Suspected only791 (87–95)56 (33–71)798 (94–100)96 (95–97)93 (85–99)90 (86–92)98 (93–100)96 (95–97)
Confirmed and suspected1291 (80–98)91 (89–93)994 (81–100)86 (81–90)95 (84–100)91 (88–94)78 (63–90)86 (80–89)
Reference standard
 NPS1296 (90–99)74 (65–81)1097 (88–100)96 (95–97)93 (80–100)93 (91–95)97 (89–100)94 (92–95)
ONPS783 (68–94)95 (93–96)696 (90–100)93 (90–95)96 (93–98)27 (0–52)81 (59–96)99 (98–99)
Gargle medium#
Saline897 (90–100)82 (76–87)696 (86–100)92 (89–94)94 (72–100)96 (94–97)92 (74–100)96 (95–97)
Water786 (70–97)94 (92–95)6100 (96–100)96 (94–97)93 (82–99)88 (84–92)96 (79–100)99 (99–99)
Sterility of gargle
Saline gargle (n=8)
  Sterile5100 (90–100)81 (72–88)391 (64–100)89 (82–93)82 (20–100)97 (96–98)92 (78–100)64 (31–81)
  Nonsterile/not mentioned391 (77–99)85 (73–92)399 (93–100)80 (63–89)99 (96–100)0 (0–86)90 (49–100)98 (98–99)
Water gargle (n=7)
  Sterile133 (19–49)-1100 (95–100)-100 (87–100)-59 (46–71)-
  Nonsterile/not mentioned692 (88–95)30 (0–55)5100 (93–100)97 (96–98)91 (79–99)91 (87–93)100 (100–100)83 (74–89)
Volume of gargle
 ≤5 mL1092 (87–95)67 (53–77)999 (95–100)95 (93–96)97 (94–99)54 (32–69)95 (88–99)97 (97–98)
 >5 mL787 (66–100)94 (92–95)593 (75–100)88 (82–92)91 (60–100)96 (94–97)74 (49–93)92 (88–94)
Duration of gargling+
 ≤10 s686 (62–100)93 (90–95)689 (72–99)81 (71–88)86 (60–100)95 (93–96)78 (50–98)93 (91–95)
 >10 s895 (90–99)76 (66–83)6100 (100–100)10 (0–44)98 (94–100)56 (30–72)98 (92–100)96 (94–97)
Positivity rate of ONPS
 <20%499 (93–100)27 (9–42)498 (87–100)99 (98–99)84 (44–100)96 (94–98)100 (99–100)4 (0–100)
 ≥20%1589 (82–95)91 (89–93)1297 (90–100)91 (88–93)96 (91–99)86 (82–89)84 (71–94)95 (94–96)
Region
European countries886 (72–97)92 (89–94)799 (91–100)94 (92–95)95 (85–100)86 (81–89)90 (71–100)97 (96–98)
North America594 (90–96)26 (0–54)4100 (100–100)34 (0–61)96 (93–98)0 (0–100)99 (98–100)61 (33–78)
Asia596 (83–100)85 (77–90)491 (74–100)90 (84–93)85 (44–100)98 (97–98)85 (73–95)79 (64–88)
Middle East182 (74–88)-190 (73–100)-98 (94–100)-47 (32–63)-
Symptomology§
Symptomatic391 (83–97)62 (28–80)188 (84–91)-65 (56–74)-96 (93–98)-
 Symptomatic and asymptomatic1391 (87–95)79 (73–84)1298 (93–100)95 (93–96)97 (95–99)56 (38–68)89 (77–98)97 (97–98)
Asymptomatic262 (9–100)94 (89–97)2100 (100–100)0 (0–98)98 (87–100)0 (0–81)86 (29–100)99 (98–99)
Included childrenƒ
Yes989 (77–97)93 (91–95)797 (91–100)94 (91–95)95 (93–97)6 (0–29)90 (76–99)98 (97–98)
No794 (85–100)77 (66–84)693 (79–100)96 (94–97)86 (59–100)96 (95–97)89 (68–100)98 (97–98)
Peer reviewed
Yes1991 (85–96)88 (86–91)1697 (92–100)96 (95–96)95 (89–99)89 (87–91)91 (81–98)98 (97–98)
No00
Target gene
1 gene592 (83–98)78 (65–86)596 (74–100)94 (92–96)94 (80–100)91 (88–94)93 (72–100)93 (90–95)
 ≥2 genes1491 (82–97)91 (88–93)1197 (91–100)96 (95–97)95 (89–99)87 (82–90)89 (77–97)98 (98–99)

PPV: positive predictive value; NPV: negative predictive value; ONPS: oropharyngeal–nasopharyngeal swab. Other regions included European countries, Mediterranean countries and Asian countries. Target gene refers to number of gene regions tested by reverse transcriptase PCR assays, i.e. assays detecting both nucleocapsid (N)1 and N2 were counted as dual targets. #: three studies did not specify the gargling medium (water or saline), and one study used bean-extract gargle. One study used sterile gargle, without specifying water or saline gargle. : two studies did not report the volume of gargling solutions. +: five studies (six study populations) did not report the duration of gargling. §: one study did not report the symptomatic status of the population. ƒ: three studies did not specify the inclusion of children population.