Background Nucleic acid amplification tests (NAATs) can now detect chlamydia (CT) and gonorrhoea (GC) but cultures are needed in GC NAAT positive people prior to treatment. This necessitates re-evaluation, examination and culture if cultures have not been taken initially.

Aim/Objective To discover if it is more cost-effective to perform a NAAT plus GC culture or just a NAAT followed by recall of GC positives for culture.

Methods 3973 women performed a self-taken vulvo-vaginal swab (VVS) then clinicians took urethral and endocervical samples for GC culture. The VVSs were analysed for GC/CT by Aptima Combo 2 (AC2). Cost effectiveness was analysed using incremental cost effectiveness ratios using correct detection of GC/CT as the primary endpoint. Costs were estimated from a sub-sample of 92 patients in July 2009 and included costs of clinic time and laboratory costs. Comparisons were made of GC cultures plus a CT NAAT vs VVSs analysed by AC2 in various subgroups.

Results VVS GC/CT NAAT with subsequent culture of GC positives was more cost-effective (8% cost-saving). The greatest saving was in women not requiring examination (37% cost saving). Cost of time taken explaining a self-taken swab was 11% of cost of examination. Savings also accrued by using AC2 rather than GC culture and CT NAAT. In contacts of GC, it was more cost-effective to include GC culture at first examination (15% cost saving).

Conclusions VVS analysed by AC2 for GC/CT is more cost-effective and detects more infections than GC culture plus CT NAAT. In women with no symptoms self-taken VVSs give cost savings of 37%. In women with symptoms VVSs remain cost-effective unless the prevalence of GC is above 10%. We would recommend including GC culture at first examination for women who are GC contacts (see abstract O2 table 1), those with pelvic inflammatory disease or cervicitis and in other circumstances where immediate antibiotic treatment is given.