Comparing SARS-CoV-2 Viral Load in Human Saliva to Oropharyngeal Swabs, Nasopharyngeal Swabs, and Sputum: A Systematic Review and Meta-Analysis

Table 7

Study characteristics of SARS-CoV-2 viral load in saliva compared with OPS, NPS, and sputum indicated by copies/mL RNA.

Author	Reference	Study design	Viral load (copies/mL RNA)	SD and IQR	Method to detect viral load	Saliva sample source	% SARS-CoV-2 positive	Total cohort size	Days onset	Symptomatic	Asymptomatic
Byrne(2020)	[32]	Cross-sectional	Saliva median: 1.83 × 10^3 mean: 6.73 × 10^3	IQR saliva: 4.64 × 10^1–1.7 × 10^4	RT-PCR	Self-collected with funnel	Saliva: 10.9%	110	NR	n = 1234	NR
			NT median: 8.52 × 10^3 mean: 1.03 × 10^5	SD saliva: 1.42 × 10^4			NT: 12.7%
				IQR NT: 5.08 × 10^1–2.76 × 10^5
				SD NT: 2.27 × 10^5
Chua (2021)	[13]	Prospective cohort	Children saliva symptomatic (mean log10): 5.8 (6.32 × 10^5 copies/mL RNA) asymptomatic saliva (mean log10): 4.5 (3.17 × 10^4 copies/mL RNA)	IQR saliva symptomatic: 4.9–6.7	RT-PCR	Spit	Saliva: 46%	91	0–18	Mean copies/mL RNA: 6.32 × 10^5	Mean copies/mL RNA: 3.17 × 10^4
			Sputum symptomatic (mean log10): 6.4 (2.51 × 10^6 copies/mL RNA)	IQR saliva asymptomatic: 3.6–5.1						IQR: 7.95 × 10^4–5.02 × 10^6n = 63	IQR 3.99 × 10^3–1.26 × 10^5n = 28
			Sputum asymptomatic (mean log10): 5.2 (1.59 × 10^5 copies/mL RNA)	IQR sputum symptomatic: 4.9–8.1
				IQR sputum asymptomatic: 3.9–6.1
Han (2020)	[55]	Case report	Saliva (mean log10): 5.5 (3.17 × 10^5 copies/mL RNA)	NR	RT-PCR	NR	100%	1	6–10	NR	NR
			Neonate OPS: 1.3 × 10^8
Hasanoglu (2021)	[56]	Prospective cohort	Saliva (mean log10): 5.18 (1.51 × 10^5 copies/mL RNA)	Saliva (min–max log10): 2.87–7.47 (7.42×10^2–2.96×10^7 copies/mL RNA)	RT-qPCR	NR	Saliva: 50% NPS: 80%	60	1–14	n = 22/45	n = 8/15
			Saliva (median log10): 5.25 (1.78 × 10^5 copies/mL RNA)	SD: 7.2 × 10^6
			NPS (mean log10): 5.23 (1.7 × 10^5 copies/mL RNA)	NPS (min–max): 2.22–7.27 (1.66 × 10^2–1.86 × 10^7 copies/mL RNA)
			NPS (median log10): 5.11 (1.29 × 10^5 copies/mL RNA)	SD: 4.2 × 10^6
Jeong (2020)	[29]	Case report	Saliva (mean log10): 1.28 (19.06 copies/mL RNA)	SD saliva: 0.28	RT-PCR	NR	Saliva: 80%	5	8–30	NR	NR
				SD NPS: 0.11			NPS: 100%
			NPS (mean log10): 1.26 (18.2 copies/mL RNA)
Li (2021)	[57]	Prospective cohort	Saliva (copies/test) mean: 5.68 × 10^3	SD saliva: 1.36 × 10^4	ddPCR	Spit	Saliva: 16.2%	37	7–69	NR	NR
			NPS (copies/test) mean: 1.62 × 10^4	SD NPS: 6.75 × 10^4			NPS: 54.1%
Moreno-contreras (2020)	[58]	Cross-sectional	Saliva median: 3.5 × 10^10	IQR NR	RT-qPCR	Spit	Saliva: 37.2%	253	NR	NR	NR
			OPS median: 3.9 × 10^8	IQR NR			NPS: 31.6%
			Saliva (CT value mean): 29 (n = 41)	SD saliva (CT value): 3.4
			OPS (CT value mean): 31.7 (n = 41)	SD OPS (CT value): 3.6
Wyllie 2020	[14]	Prospective cohort	Saliva mean: 5.69 × 10^11	SD saliva: 2.97 × 10^12	RT-PCR	Self-collected (spit repeatedly in sterile urine cup, excluding bubbles)	Saliva: 29.6% NPS: 32.4%	142	2–34	Saliva copies/mL RNA mean: 5.69 × 10^8	Saliva copies/mL RNA mean: 6.38 × 10^4
			NPS mean: 8.22 × 10^10	SD NPS: 4.5 × 10^11						SD: 2.97 × 10^9n = 39	SD: 3.8 × 10^4n = 3
			Saliva (CT value mean): 31.5	SD saliva (CT value): 8.1						Saliva CT-value mean: 23.77	Saliva CT-value mean: 23.69
			NPS (CT value mean): 35.8	SD NPS (CT value): 6.4						SD: 2.25 n = 44	SD: 2.89 n = 90

All median values, if present, are original and obtained from the publication. Authors were contacted for the original dataset. NR = not reported, ND = not detected, NT = nasal-throat, NPS = nasopharyngeal swab, OPS = oropharyngeal swab, SD = standard deviation, and IQR = interquartile range.