Lessons from a one-year hospital-based surveillance of acute respiratory infections in Berlin- comparing case definitions to monitor influenza

Table 4 Comparison of case definitions (CD) for hospitalized respiratory infections (RI) according to their ability to capture pH1N1-positive cases

	Case definition	Cases from entire study period			Cases from study period 1
		Sensitivity	Specificity	Area under ROC (95% CI)	Sensitivity	Specificity	Area under ROC (95% CI)
Swabbing interval ≤ 4 days	CD4	55%	59%	0.57 (0.45-0.69)	56%	63%	0.59 (0.42-0.77)
	CD2	95%	26%	0.60 (0.54-0.66)	100%	44%	0.72 (0.59-0.84)
	CD3	90%	41%	0.65 (0.57-0.73)	94%	44%	0.69 (0.55-0.83)
Swabbing interval ≤ 7 days	CD4	55%	57%	0.56 (0.45-0.68)	56%	59%	0.57 (0.42-0.73)
	CD2	95%	22%	0.59 (0.53-0.64)	100%	38%	0.69 (0.60-0.78)
	CD3	90%	35%	0.63 (0.55-0.70)	94%	41%	0.68 (0.57-0.79)

Sensitivity, specificity, area under the receiver operator curve (ROC), percentage of pH1N1-positives captured for study period 1 (significant influenza virus circulation in Berlin) and the entire study period (gold standard: PCR confirmation of pH1N1 infections)
*Cases testing negative were only included as pH1N1-negative if the interval from symptom onset to swabbing was ≤ 4 days or ≤ 7 days, respectively. Highest ROC area in bold.

ISSN: 1471-2458