Purpose-To evaluate the ability of ophthalmologists to predict the laboratory results of presumed microbial keratitis and to explore which findings might influence diagnostic prognostication.
Design-Prospective cross-sectional study.Methods-Fifteen ophthalmologists completed study forms at the initial presentation of patients with presumed microbial keratitis. After predicting the category of microbial recovery, clinicians submitted corneal scrapings for masked laboratory processing. The relative effects of ocular inflammatory signs on correct microbial diagnosis were explored with Poisson regression.Results-Clinical examiners correctly predicted the presence or absence of microbial recovery in 79 (76%) of 104 ulcerative keratitis and successfully distinguished among bacterial, fungal, and amoebic keratitis for 54 (73%) of 74 culture-positive infections, although only 31 (42%) were properly subcategorized. The positive predictive value of clinical diagnosis was 65% (95% confidence interval (CI), 43%-84%) for 20 eyes with Pseudomonas keratitis, 48% (95% CI, 32%-63%) for 38 other bacterial keratitis, 45% (95% CI, 17%-77%) for 13 fungal keratitis, and 89% (95% CI, 52%-100%) for nine Acanthamoeba keratitis. The recognition of Pseudomonas keratitis was significantly improved by the occurrence of a larger infiltrate (P = .02), and correctly predicting Acanthamoeba keratitis was enhanced by observing a ring infiltrate (P < .001). Antimicrobial use before referral significantly attenuated clinical diagnosis (P = 0.03) and hampered microbial recovery (P = 0.004).
Conclusions-EstablishedPseudomonas keratitis and Acanthamoeba keratitis can be suspected before laboratory confirmation, but overlapping inflammatory features and recent empiric antimicrobial treatment limits etiologic recognition of most microbial corneal infections.The clinical diagnosis of microbial keratitis often relies on a history of infectious exposure and the morphological features of corneal inflammation. 1 Ophthalmologists use clinical clues to recognize ocular surface infection, 2 and some distinctive though not pathognomonic signs may help to differentiate bacterial, fungal, and amoebic pathogens of the cornea. 3-5Laboratory demonstration of the infective agent in a corneal sample is recommended 6 but may not be regularly obtained due to time, cost, and availability. 7, 8 Initial antimicrobial therapy is often guided by subjective interpretation of presenting clinical features. 9 We aimed to determine the predictive value of ophthalmologists' opinions about presumed microbial keratitis before microbiological tests were known. We also sought to identify which findings Inquiries to Kirk R. Wilhelmus, MD, Sid W. Richardson Ocular Microbiology Laboratory, Cullen Eye Institute, 6565 Fannin Street, Baylor College of Medicine, Houston, TX 77030; fax: 713-798-4142; e-mail: kirkw@bcm.tmc.edu Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this ...
