Calcium alginate swab versus Bard Parker blade in the diagnosis of microbial keratitis

Abstract

A prospective comparative evaluation of Bard Parker blade no. 15 and calcium alginate swab in the collection of corneal material was conducted. The study group included 30 consecutive cases of bacterial (n = 17), fungal (n = 11), and mixed (n = 2) cases of microbial keratitis. The samples collected by blade and swab were processed in an identical manner for viable colony counts. The yields from blade and swab were compared using the proportion test, taking into consideration the mean counts of each organism. The swab yielded significantly greater growth than blade (p = 0.003) in mycotic ulcers. However, the two patients (2/11) who showed no growth by blade but were positive by swab had smears positive and were diagnosed as mycotic ulcers. The difference between the two methods was not significant for bacterial and mixed ulcers. Replacement of blade with calcium alginate swab did not appear to be advantageous for the investigation of infectious keratitis.