Detection of antiendometrial antibodies in patients with endometriosis: methodological issues

OBJECTIVE: To determine if methodological reasons explain previous inability of a single investigator to detect antiendometrial antibodies in patients with endometriosis by indirect immunofluorescence (IIF). DESIGN: Sera of selected patients were tested by standard IIF and recently reported methodology. Alternate diluent experiments were conducted to explain discordant results. SETTING: Sera were obtained preoperatively, and testing was completed in an institutional research laboratory. Results are compared with surgical findings. PATIENTS/PARTICIPANTS: Patients, seven with endometriosis and six without endometriosis, 40 years of age or less who are presenting for gynecological surgery. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Indirect immunofluorescence was graded according to the presence or absence of cytoplasmic staining, intensity of the staining, and the lowest dilution at which staining was observed. RESULTS: The standard IIF method repeatedly demonstrated the presence of cytoplasmic staining for the presence of antiendometrial antibodies in patients with endometriosis, whereas modified methods did not produce similar positive staining results. During the alternate dilution experiments, when fluorescein isothiocyanate conjugate (FITC) was diluted in animal sera, negative results were obtained. CONCLUSIONS: The variations used in alternate methodology and failure to titrate FITC reported by other investigators are possible reasons for false-negative results reported.