Canadian Journal of Infectious Diseases and Medical Microbiology

Review Article

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

Table 4

Study characteristics of SARS-CoV-2 viral load in saliva compared with OPS, NPS, and sputum indicated by C_T value.


Author	Reference	Study design	Viral load (C_Tvalue)	SD and IQR	Method to detect viral load	Saliva sample source	% SARS-CoV-2 positive	Total cohort size	Days onset	Symptomatic	Asymptomatic

Babady (2021)	[10]	Cross-sectional	Saliva mean and median: 27.9	SD saliva: 11.1	RT-PCR	Bringing up saliva from the back of the throat and gargling	Saliva: 12.3% OPS: 10.5% NPS: 11.6%	285	NR	NR	NR
			OPS mean: 28.6 median: 28.9	IQR saliva: 22.2–36.6
			NPS mean: 21.75 and median: 22.6	SD OPS: 6.3
				IQR OPS: 24.2–32.3
				SD NPS: 4.5
				IQR NPS: 18.5–24.3

Can (2021)	[12]	Retrospective cohort	Saliva median: 29.89; mean: 29.9	IQR: 28.54–31.27	RT-PCR	Drooling	Saliva: 0.33%	4812	0–12	NR	NR
			Sputum median: 30; mean: 32.1	SD: 2.2			Sputum: 0.25%
			Oronasopharynx: median: 25.5; mean: 26.6	IQR: 25.85–39.92
				SD: 11.8			Oronasopharynx: 0.25%
				IQR: 17.37–36.74
				SD: 16.2

Colavita (2020)	[40]	Case report	Saliva mean: 39.6	SD saliva: 5.86	RT-PCR	NR	Saliva: 100%	2	0–30	NR	NR
			NPS mean: 39.15	SD NPS: 9.26			NPS: 100%
			Throat mean: 34.85	SD throat swab: 7.01			Throat: 100%
			Sputum: 32.1	SD sputum: 12.36			Sputum: 50%

Fan (2020)	[41]	Cross-sectional	Hock-a-loogie saliva median: 30; sputum median: 31	IQR NR	RT-PCR	Deep cough 3–5 times and then spitting hock-a-loogie saliva	88.90%	42	8	NR	NR
			Throat: median: 35	SD NR
			Mean of samples: NR

Hanege (2020)	[34]	Cross-sectional	Saliva mean: 30.97	SD saliva: 1.56	RT-PCR	NR	Saliva: 76.3% NPS: 100%	38	NR	Saliva C_T value mean: 31.27	Saliva C_T value mean: 29.73
			NPS mean: 27.98	SD NPS: 4.29						SD: 1.74 n = 15	SD: 0.7 n = 4

Justo (2021)	[42]	Retrospective cohort	Saliva mean: 26.48	SD saliva: 5.65	RT-PCR	Self-collection in sterile tube, avoiding mucous secretions from the oropharynx and sputum	Saliva: 52.63%	76	1–9	n = 76 viral load: NR	ND
			NPS mean: 21.42	SD NPS: 4.10			NPS: 54%

Kim (2020)	[43]	Cross-sectional	Saliva median: 32 mean: 32.8	IQR saliva: 28–38	rRT-PCR	Self-collection using spectrum solutions LLC SDNA-1000 saliva collection device	Saliva: 53% NPS: 93%	15	1–11	Saliva C_T value mean: 31.76	Saliva C_T value mean 37.57
			NP/OP median: 33; mean: 31.5	SD saliva: 8.9			Sputum: 53%			SD: 5.55 n = 13	SD: 6 n = 2
			Sputum median: 29	IQR NP/OP: 27–35
			Mean: 30.5	SD NP/OP: 6.6
				IQR sputum: 24–38
				SD sputum: 12.5

Pasomsub (2021)	[44]	Cross-sectional	Saliva median ORF1ab: 32.7; mean: 32	IQR orf1ab saliva: 28.5–35	RT-PCR	Self-collection in sputum collection container (void of coughing)	Saliva: 9% NPS/throat: 9.5%	200	2–11	NR	NR
			median N gene: 31.8	SD: 5.2
			Mean: 31.3	IQR N gene saliva: 28.4–33.7
			NPS/throat median ORF1ab: 32 mean: 31.2	SD: 4.3 IQR ORF1ab NPS/throat: 27.4–34.3
			median N gene: 30.5	SD: 5.5
			Mean: 29.6	IQR N gene NPS/throat: 26.1–32.3
				SD: 5

Procop (2020)	[45]	Cross-sectional	Saliva mean: 24.16	SD saliva: 4.80	RT-PCR	Saliva collected via spitting, via nose (by “snuffing” or “snorting” to pull nasal secretion into mouth) and via coughing to produce phlegm or secretions	Saliva: 18.06%	216	NR	n = 216 viral load: NR	ND
			NPS mean: 20.55	SD NPS: 5.36			NPS: 17.6%

Teo (2021)	[46]	Prospective cohort	Saliva tests (n = 209) mean: 26.7	SD saliva: 4.5	RT-PCR	Tilt head back, clear the throat and nose, and spit the saliva into the collection bottle. The steps were repeated until the required volume (2 mL) was achieved	Saliva: 62%	200	0–33	Saliva tests (n = 145)	Saliva tests (n = 64)
			NPS tests (n = 150) mean: 30.07	SD NPS: 4			NPS: 44.5%	(337 sets of tests)		C_T value mean: 25.7	C_T value mean: 28.4
										SD: 4.6	SD: 4.7
										Patients (n = 88)	Patients (n = 112)

Yee (2021)	[15]	Prospective cohort	Saliva samples (n = 127) mean: 21.5	Range saliva: 17.9–26.3	qRT-PCR	Gently rubbing the outside of the cheeks and spitting without coughing or clearing throats	Saliva: 26.33%	300	0–43	n = 30	n = 30
			NPS samples (n = 127) mean: 23.8	SD: 2.1			NPS: 29%			Viral load: NR	Viral load: NR
				Range NPS: 21.3–29.0
				SD: 1.93

Yokota (2021)	[47]	Prospective cohort	Saliva median: 28.9 mean: 28.51	IQR saliva: 23.1–33.6	qRT-PCR	Self-collected	Saliva: 90% NPS: 81%	42	1–12	n = 42	ND
			NPS median: 27.4; mean: 28.15	SD saliva: 8.09						Viral load: NR
				IQR NPS: 21.3–35.6
				SD NPS: 11.07

Yoon 2020	[48]	Case report	Saliva mean: 31.41	SD saliva: 6.37	rRT-PCR	Self-collected	Saliva, NPS, OPS, and sputum 100%	2	1–9	n = 2	ND
			NPS mean: 25.59	SD NPS: 6.49						Viral load: NR
			OPS mean: 30.51	SD OPS: 4.84
			Sputum mean: 26.55	SD sputum: 4.67

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