Utility of Microbiologic and Histopathologic Assessment of Corneal Biopsies in the Evaluation of Microbial Keratitis

Abstract

Purpose: : To investigate the utility of corneal biopsy in the evaluation of non-healing microbial keratitis; to compare results of microbiologic and histopathologic studies from the same biopsy specimens; and to identify factors related to positive biopsy results.

Methods: : Retrospective review of medical records and pathology data for all patients who underwent diagnostic corneal biopsy because of microbial keratitis at the Jules Stein Eye Institute from June 1991 through June 2005. Agreement between culture and light microscopy results was analyzed. Lesion size, evidence of lesion progression, and interval from initial evaluation at UCLA to biopsy were analyzed as potential predictors of positive biopsy results.

Results: : Biopsies for a total of 34 consecutive patients were identified. Both microbiologic and histopathologic results from the same biopsy specimen were available for 31 patients. Organisms were identified in 15 of 34 biopsies (44%; culture positive: 9/33 [27%]; histopathology positive: 14/32 [44%]). Corneal biopsy revealed microorganisms in seven of 16 patients with negative cultures from scrapings obtained at presentation. Among eight biopsies for which both culture and histopatholgic examination were positive, discordant results were found in six; in each, cultures grew bacteria, while histopathologic examination revealed cysts or fungi, which had not grown on culture. Both culture and histopathologic examination were negative for 18 biopsies. Larger lesions were associated with positive biopsy results (p= 0.018, T-test). Patients with progression of keratitis were not more likely to have a positive biopsy than those without enlargement or new foci (p=0.252, Fisher exact test). There was no evidence that a longer duration from initial evaluation to biopsy was associated with negative biopsy results (p=.205, Kruskal-Wallis test).

Conclusions: : Microbiologic cultures and histopathologic examination are both useful in the evaluation of biopsy specimens obtained from patients with microbial keratitis. Each technique can provide complementary or unique information regarding infection, and biopsy can provide information not obtained by culture of scrapings obtained at presentation. A delayed biopsy does not appear to reduce the yield of positive biopsies in cases of non-healing microbial keratitis.

Keywords: cornea: clinical science • keratitis • pathology: human