Table 5.

Accuracy of Simple Heuristics for the Clinical Diagnosis of Influenza

Rule and Study^a	Heuristic	Sensitivity, %	Specificity, %	PPV, %	NPV, %	LR+	LR−	LR+/ LR−
ILI=influenza-like illness; LR− = negative likelihood ratio; LR+ = positive likelihood ratio; NPV = negative predictive value; PPV = positive predictive value; RTI=respiratory tract infection.
^a Study population and prevalence of influenza are shown in Table 2.
^b Odds ratio in logistic regression model was 6.7 for cough and 3.1 for temperature greater than 38°C.
^c Odds ratio in logistic regression model was 7.2 for cough, 4.3 for headache, and 3.9 for pharyngitis.
Fever and cough rule
Stein et al,⁸ 2005	Fever (≥37.8°C) and cough	40	92	58	84	5.1	0.7	7.3
Govaert et al,¹³ 1998	Fever (>38°C) and cough	30	94	26	95	5.0	0.74	6.8
Boivin et al,¹² 2000^b	Fever (≥37.8°C) and cough	78	55	87	39	1.7	0.4	4.3
Monto et al,¹¹ 2000	Fever (≥37.8°C) and cough	64	67	79	49	1.94	0.54	3.6
van den Dool et al,²² 2008	Fever (>38.3°C) and cough	42	90	26	95	4.2	0.64	6.5
Fever, cough, and acute onset rule
Stein et al,⁸ 2005	Fever (≥37.8°C), cough, and duration ≤48 hr	75	89	65	93	6.5	0.3	21.7
Walsh et al,²¹ 2002	Fever (≥38°C), cough, and duration <7 days	78	73	47	91	2.9	0.3	9.7
Govaert et al,¹³ 1998	Fever (>38°C), cough, and acute onset	27	95	30	95	5.9	0.76	7.8
Monto et al,¹¹ 2000	Fever (≥37.8°C), cough, and acute onset	63	68	77	51	1.95	0.54	3.6
Cough, headache, and pharyngitis rule
Friedman and Attia,²⁰ 2004^c	Cough, headache, and pharyngitis	80	78	77	81	3.7	0.26	14.2