Table 4.

Analysis of timing and site of swabs.

	Timing (36 v 32 weeks)			Site (Either Lower Vaginal or Perianal vs Lower Vaginal Swab alone)
	Difference (36 – 32)	95% Confidence Interval	p-value	Difference (Either vs LVS)	95% Confidence Interval	p-value
Sensitivity	8.8%	(1.2%, 16.3%)	0.023*	8.2%	(4.6%, 11.7%)	<0.001†
Specificity	0.6%	(-1.2%, 2.5%)	0.493	-1.8%	(-2.6%, -0.9%)	<0.001§/P >
Negative Predictive Value	2.3%	(0.3%, 4.3%)	0.026*	2.0%	(1.0%, 3.0%)	<0.001†
Positive Predictive Value	3.6%	(-2.8%, 9.9%)	0.269	-3.1%	(-5.8%, -0.5%)	0.019§/P >
Likelihood Ratio +	1.62	(-2.69, 5.92)	0.462	-1.59	(-3.68, 0.49)	0.134
Likelihood Ratio -	-0.09	(-0.18, -0.01)	0.021*	-0.08	(-0.12, -0.04)	<0.001†
Diagnostic Odds Ratio	14.3	(-8.06, 36.8)	0.210	3.63	(-4.99, 12.2)	0.409

* favours swabs taken at 36 weeks over 32 weeks

† favours either site over LVS only

§favours LVS only over either site