Accuracy of Current Diagnostic Criteria for Acute Bacterial Infection in Older Adults in the Emergency Department

Abstract

Objectives: To compare the accuracy of the Loeb criteria, emergency department (ED) physicians' diagnoses, and Centers for Disease Control and Prevention (CDC) guidelines for acute bacterial infection in older adults with a criterion standard expert review.

Design: Prospective, observational study.

Setting: Urban, tertiary-care ED.

Participants: Individuals aged 65 and older in the ED, excluding those who were incarcerated, underwent a trauma, did not speak English, or were unable to consent.

Measurements: Two physician experts identified bacterial infections using clinical judgement, participant surveys, and medical records; a third adjudicated in cases of disagreement. Agreement and test characteristics were measured for ED physician diagnosis, Loeb criteria, and CDC surveillance guidelines.

Results: Criterion-standard review identified bacterial infection in 77 of 424 participants (18%) (18 (4.2%) lower respiratory, 19 (4.5%) urinary tract (UTI), 22 (5.2%) gastrointestinal, 15 (3.5%) skin and soft tissue). ED physicians diagnosed infection in 71 (17%), but there were 33 with under- and 27 with overdiagnosis. Physician agreement with the criterion standard was moderate for infection overall and each infection type (κ = 0.48-0.59), but sensitivity was low (<67%), and the negative likelihood ratio (LR(-)) was greater than 0.30 for all infections. The Loeb criteria had poor sensitivity, agreement, and LR(-) for lower respiratory (50%, κ = 0.55; 0.51) and urinary tract infection (26%, κ = 0.34; 0.74), but 87% sensitivity (κ = 0.78; LR(-) 0.14) for skin and soft tissue infections. CDC guidelines had moderate agreement but poor sensitivity and LR(-).

Conclusion: Emergency physicians often under- and overdiagnose infections in older adults. The Loeb criteria are useful only for diagnosing skin and soft tissue infections. CDC guidelines are inadequate in the ED. New criteria are needed to aid ED physicians in accurately diagnosing infection in older adults.

Keywords: diagnosis; emergency department; geriatric; infection; urinary tract infection.