• PURPOSE: To assess the usefulness of diagnostic tests that are performed on vitrectomy specimens from patients with suspected lymphoma or infection. • DESIGN: Noncomparative, retrospective, interventional case series. • METHODS: Seventy-eight consecutive patients (84 eyes) underwent pars plana vitrectomy for diagnostic purposes. Vitrectomy with cytologic, cytofluorographic, or microbiologic analysis of vitreous samples was performed. The main outcome measures were the efficiency of diagnostic procedure and positive and negative predictive values (PPV and NPV). • RESULTS: There were 28 patients (33 eyes) with suspected intraocular lymphoma and 50 patients (51 eyes) with suspected infection, which was subdivided into chronic endogenous endophthalmitis, atypical chorioretinitis, or chronic postoperative inflammation. Vitreous testing led to a diagnosis in 48 of 78 patients (61.5%); 14 patients with a final diagnosis of lymphoma/leukemia, and 34 patients with a final diagnosis of infection. When preoperative indication was compared with final clinical diagnosis, the efficiency of the diagnostic procedure of cytologic evaluation, flow cytometry, and bacterial/fungal culture was 67%, 79%, and 96%, respectively. For lymphoma, the PPV of cytologic evaluation was 100% and the NPV 60.9%. For infection, the PPV of bacterial/fungal culture was 100% and the NPV 94.9%. CD22+ B lymphocytes <20% of total cells on cytofluorographic analysis had a PPV of 88% for lymphoma. A cytofluorographic CD4:CD8 T-lymphocyte ratio <4 had a PPV of 70% for immunologically mediated uveitis. Surgical complications were rare and manageable. • CONCLUSION: Diagnostic vitrectomy in selected patients with carefully planned testing is an effective means of supporting diagnoses in intraocular lymphoma, chronic intraocular infections, and atypical chorioretinitis. Flow cytometry quantitates the percentages and ratios of various cell types and is helpful in contrasting intraocular lymphoma with immunologically mediated uveitis.
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