Table 2.

Author-reported limitations, by topic

Reported limitationa	Examples	No. of reporting limitations (n = 71)	Potential bias (under- or overestimation)
Results not generalizable outside study setting/population	Restricted geographic coverage; population restrictions (e.g. hospitalized or medically attended patients only); assessment of single season	29	Under or over
Sampling period	Sampling not tailored to RSV season (e.g. use of influenza season)	18	Under
	Sampling gaps within study period
Sample size	Small sample size leading to unstable estimates	11	Under or over
Testing method	Quality or sensitivity issues relating to PCR testing	10	Under
	Lack of serology
Not testing all eligible population	Significant proportion not sampled	10	Under (incidence)
Suboptimal case definitions	Definitions of ARI, ILI or choice of required symptoms for inclusion may miss RSV cases, as RSV may not feature fever or cough	9	Under
Duration between enrolment and viral testing	Viral shedding reduces over time and virus may disappear from sample site	5	Under
Sampling method	Single sampling site (e.g. nasopharyngeal only; serology only)	5	Under
	Suboptimal duration or method of sample storage

ARI, acute respiratory illness; ILI, influenza-like illness; RSV, respiratory syncytial virus

^aOnly issues specifically reported by study authors as limitations are included