Pitfalls of internet-accessible diagnostic tests: inadequate performance of a CE-marked Chlamydia test for home use

Abstract

Objectives: To evaluate the performance of a Conformitée Européenne (CE)-marked home test for Chlamydia trachomatis (CT) that is available over the internet.

Methods: A total of 231 eligible women attending the Social Hygiene Clinic (SHC) or Obstetrics-Gynecology (OB-GYN) Clinic in Iloilo City, Philippines were recruited to an evaluation of the HandiLab-C Chlamydia home test (HandiLab-C). One vaginal swab was tested with HandiLab-C on-site and the second in Cambridge, UK with two nucleic acid amplification tests (NAAT), the Roche Amplicor and Abbott m2000. The organism load of NAAT-positive swabs was quantified.

Results: Concordance between the NAATs was high (kappa agreement: 0.984). Using the Abbott assay as the gold standard, the sensitivity and specificity of the Roche assay were 97.4% and 100%, respectively. CT prevalence by Abbott was 8.0% (8/100) in the OB-GYN Clinic and 23.7% (31/131) at SHC. The sensitivity of HandiLab-C was 12.5% (1/8) and 19.4% (6/31) in OB-GYN and SHC respectively, with specificities of 93.5% (86/92) and 88% (88/100) respectively. Overall positive and negative predictive values of HandiLab-C were 28% and 84.5% respectively. No correlation between HandiLab-C performance and organism load (range: 1.3 x 10(2) to 1.4 x 10(7) bacteria/swab) was observed.

Conclusions: The performance of HandiLab-C is very poor, with the test yielding more false-positive (18/193) than true-positive (7/38) results. It remains accessible via the internet under various brand names and has retained its CE mark. This situation raises serious concerns about the regulation of diagnostic products available via the internet and the standards of certain Notified Bodies that issue the CE mark.