Diagnóstico molecular das infecções por Chlamydia trachomatis e Neisseria gonorrhoeae: avaliação do desempenho do swab vaginal

• Autor(a) principal: Cardoso, Fernanda Alves de Brito e
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/4808
• topic: C. trachomatis; N. gonorrhoeae; PCR; Desempenho; Urina; Swab endocervical; Swab vaginal; C. trachomatis; N. gonorrhoeae; Prevalence; Urine; Endocervical swab; Vaginal swab; Performance; IMUNOLOGIA::IMUNOLOGIA APLICADA

The introduction of the nucleic acid amplification tests (NAATs) was a major breakthrough in the screening for the sexually transmitted diseases (STD) caused by Chlamydia trachomatis and Neisseria gonorrhoeae because they are highly sensitive and they can be used with noninvasive specimens, such as urine. The use of urine has made it far easier to test asymptomatic individuals and has also made it possible to perform epidemiological studies in places other than clinical settings. Many studies have shown also that vaginal swab can be used for detection of both infections, however, just the NAAT Aptima Combo 2 has been cleared by Food and Drug Administration for this specimen use. In Brazil, the most widely used NAAT for the diagnosis of chlamydia and neisseria is the kit Amplicor CT/NG (Roche) and, up to date, there isn’t any study which evaluates the use of vaginal swabs. Objectives: To evaluate the performance of the kit AMPLICOR CT/NG (Roche) in the diagnosis of C. trachomatis and N. gonorrhoeae using urine, endocervical and vaginal swabs and to analyze the agreement of results between the different biological specimens. Methods: The target population was sexually active adolescents and young women between 15 and 24 years from Inhumas, Goias. Socio-demographic and sexual behavior were obtained through a face-to-face interview. The diagnosis was performed by PCR using the AMPLICOR CT/NG (Roche) assay in urine, vaginal swab (VS) and endocervical swab (ES) specimens. For the performance evaluation were calculated the sensitivity, specificity, positive predictive value and negative predictive value. The kappa coefficient was calculated to assess agreement between the samples. It was considered a true-positive result when at least two of three biological samples from the same patient were positive for chlamydia and/or gonococcus. Results:Among the 428 participants the mean age was 19,4 years. The three biological specimens were collected from 309 adolescents (72.2%). Among these, the prevalence rates were 8.7% (IC95% 5,8-12,4) for C. trachomatis and 2.3% (IC95% 0,9-4,6) for N. gonorrhoeae.For chlamydia the sensitivities observed with the different samples were above 80% and specificities exceeding 97% with positive predictive values (PPV) between 78.8% and 84.6% and negative predictive values (VPNs) >98%. For the gonococcus the sensitivities were 42.8% for urine, 71.4% for ES and 100% for VS with specificities >96% for the three samples. The two types of swab showed low PPVs for gonococcus (≈40%) and urine showed PPV of 100%. VPNs were >98%. The agreement of results between specimens was around 94% for the detection of both infections. However, the values of kappa (κ) coefficient ranged from 0.68 to 0.73 for chlamydia, which means substantial agreement between samples. For gonococcal infection, the agreement was slight or fair with κ coefficients ranging from 0.13 to 0.33. Conclusions:The performances of the specimens and the κ values suggest that the vaginal swab appears to be equivalent to urine and endocervical swab for detection of chlamydia and may be suitable for screening studies. The three samples showed different performance in the detection of gonococcus and did not present good agreement of results, suggesting that they are not equivalent in the diagnosis of this infection with the PCR kit used.