Performance characteristics of clinical diagnosis, a clinical decision rule, and a rapid influenza test in the detection of influenza infection in a community sample of adults.
OBJECTIVE
The accurate diagnosis of influenza remains a diagnostic dilemma. We examine the performance of various strategies for diagnosing influenza infection in an unselected sample of adults during influenza season.


METHODS
Consecutive adults presenting to a university emergency department or urgent care clinic between January and March 2002 with acute respiratory complaints were eligible for this prospective observational study. The performance of clinician judgment, a rapid influenza test, and a clinical prediction rule in predicting influenza infection was evaluated using referent standard of reverse transcriptase polymerase chain reaction. Statistical significance was assessed using McNemar's test of proportions.


RESULTS
Fifty-three of 258 (21%) patients had a positive influenza reverse transcriptase polymerase chain reaction test. Overall, clinician judgment showed sensitivity of 29% (95% confidence interval [CI] 18% to 43%) and specificity of 92% (95% CI 87% to 95%). The rapid influenza test showed a sensitivity of 33% (95% CI 22% to 47%) and specificity of 98% (95% CI 96% to 99%). The clinical prediction rule showed a sensitivity of 40% (95% CI 27% to 54%) and specificity of 92% (95% CI 87% to 95%). Clinician judgment when patients presented within 48 hours showed a sensitivity of 67% (95% CI 39% to 86%) and specificity of 96% (95% CI 81% to 99%). Neither the rapid influenza test (P=.10) nor the clinical prediction rule (P=.42) was superior to clinician judgment alone in the diagnosis of influenza.


CONCLUSIONS
The suggestion that a clinical decision rule or a rapid influenza test is better than clinical judgment alone for the diagnosis of influenza in an unselected patient population is not supported by this study.
Stein
John
J
Division of Emergency Medicine, University of California, San Francisco, CA 94143, USA. jstein@medicine.ucsf.edu
Louie
Janice
J
Flanders
Scott
S
Maselli
Judith
J
Hacker
Jill K
JK
Drew
W Lawrence
WL
Gonzales
Ralph
R
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002983:Clinical Competence; D019411:Clinical Laboratory Techniques / Q000379:methods; D017714:Community-Acquired Infections / Q000175:diagnosis; D003661:Decision Support Techniques; D004635:Emergency Medicine / Q000295:instrumentation* / Q000379:methods*; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D017064:Process Assessment, Health Care; D011446:Prospective Studies; D012680:Sensitivity and Specificity