SENSITIVITY AND PREDICTABILITY OF VITREOUS CYTOLOGY, BIOPSY, AND MEMBRANE-FILTER CULTURE IN ENDOPHTHALMITIS

Purpose: Forty-seven consecutive patients with endophthalmitis were pr ospectively studied to: 1) compare the undiluted vitreous biopsy cultu re and membrane filter culture of vitrectomy cassette fluid; 2) determ ine the sensitivity and specificity of initial smear examinations in r elation to final culture; and 3) characterize vitreous cytology in cul ture positive and negative endophthalmitis. Methods: Examinations incl uded smears (Gram stains, Diff Quik [Bacto Laboratories Pvt. Ltd., Liv erpool, Australia] and unstained) and aerobic/anaerobic culture of und iluted vitreous biopsy specimens and diluted vitreous collected in the cassette, The cassette fluid was passed through 5-mu m polycarbonate filter for cytology and a 0.22-mu m polyvinylidene difluoride millipor e filter for culture, Results: By either method culture results were p ositive in 27 (57.4%) patients, Culture positivity of the vitreous bio psy alone was 44.6% and cassette fluid alone was 49% (P > 0.05), In th e initial smear examination the sensitivity and specificity of the Gra m stain were 66.6% and 84.2%, respectively. Comparatively, Diff Quik p rovided lower sensitivity and specificity at 40.7% and 80.9% respectiv ely, Examination of wet film of vitreous samples did not provide any u seful information, Although polymorphs were seen in large numbers in a ll cultures that yielded positive results on examination, they also we re seen in 80% of the sterile samples. There was no significant differ ence in the quantity of macrophages observed in infected and noninfect ed samples. Conclusions: Initial smear examination and cytology have l imited roles in the diagnosis of infectious endophthalmitis, Obtaining cultures of both an undiluted vitreous biopsy sample and the vitrecto my cassette fluid has a significant advantage compared with culture of only one sample.