P3-S1.12 High concordance of test results of theChlamydia trachomatisdetection and genotyping kit compared to the COBAS Amplicor CT/NG test
Authors: van Dommelen L , Brink A A T P , van Tiel F H , Quint W G V , Morré S A , Wolffs P F , Hoebe C C J P A 
Published: July 2011

Background

Improving diagnostic methods for the detection ofChlamydia trachomatis(CT), including genotyping, can contribute to control of CT by acquiring knowledge on epidemiology, transmission, sexual networks and pathogenicity. In the present study, we have compared the performance of theChlamydia trachomatisdetection and genotyping (Ct-DT) kit (Labo Bio-medical Products BV, Rijswijk, The Netherlands) with the COBAS Amplicor CT/NG (Roche Diagnostics Systems, Basel, Switzerland) in a well described female population consulting a sexually transmitted infection (STI) clinic.

Methods

Self obtained vaginal swabs (SVS) were collected from females visiting a STI clinic. The presence ofChlamydia trachomatisDNA was determined by the COBAS Amplicor CT/NG. In agreement with the manufacturer, 200 μl of processed COBAS Amplicor CT/NG medium was used for DNA isolation using the Qiagen DNA mini kit (Qiagen GmbH, Hilden, Germany). For the Ct-DT kit, 10 μl DNA was used. All CT positive samples were used for serovar typing. Discrepant samples were retested using COBAS TaqMan CT Test v2.0 (Roche Diagnostics Systems, Basel, Switzerland). A sample was considered CT positive (comparison standard) if both NAAT were positive or if one these NAAT and the retest was positive.

Results

In all, 772 clients were included in the original study. COBAS medium was available from 71 CT positive clients and 179 CT negative samples were randomly selected. With the Ct-DT kit, 68 out of 71 CT positive samples (97%) tested positive and one borderline, leaving two discrepant results. Retesting of the latter two samples using the COBAS TaqMan assay resulted in two positive tests. All COBAS Amplicor CT negative samples were also negative with the Ct-DT kit. The sensitivity, specificity, positive and negative predictive value of the Ct-DT kit were 97%, 100%, 100% and 99%, respectively, if the borderline result is included in the positive results. Genotyping results are presented in Abstract P3-S1.12 table 1. Serovars D/Da, E and F were most prevalent. The serovar distribution is comparable to previously published Dutch data.

Abstract P3-S1.12 Table 1

Nucleic acid amplification test results, including serovar distribution

COBAS AmplicorDEIARHA SerogroupRHA SerovarCOBAS TaqManFinal conclusionNPositivePositiveBD/DaNAPositive4ENAPositive37*IFNAPositive18†G/GaNAPositive3CI/IaNAPositive2JNAPositive1None detectedPositivePositive1None detectedNone detectedPositivePositive1BorderlineBNone detectedNegativePositive1NegativeNANAPositivePositive2NegativeNegativeNANANANegative179Total250*

One double infection with serogroup C, serovar K.

†

One double infection with serogroup C (no serovar detected).

Conclusion

Compared with COBAS Amplicor CT/NG, theChlamydia trachomatisdetection and Ct Genotyping RHA Kit combination is a sensitive and highly specific assay to detectChlamydia trachomatis. Moreover, it is a more rapid and easy to perform method to detect the most commonly detected serotypes compared to PCR-RFLP typing.