Identification of the cutoff point for IgG antibodies in Chlamydia trachomatis infection

Objective: To establish the cutoff point of antibodies IgG titres (indirect immunofluorescence) for Chlamydia trachomatis. Methods: This is a retrospective study with 204 electronic records of patients attended at a university and private infertility center in the city of Goiania, in the period of 2006 to 2009. The sensitivity and the specificity of the test were calculated by ROC analysis through BioEstat (R) software using the standard methodology. Results: The best cutoff point of the ROC curve with the titre was 1:64. However, we believe that we can continue using a cutoff titre to >= 1:16 by interfering little in sensitivity and specificity and because it is currently used in the Clinical Laboratory of Hospital Clinics of the Federal University of Goias. Conclusion: The fact of having a population complaining of infertility allowed use of the ROC curve for determining the cutoff point, optimizing, the sensitivity and specificity of the test.