Pitfalls of internet-accessible diagnostic tests: inadequate performance of a CE-marked Chlamydia test for home use
- 1Diagnostics Development Unit, Department of Haematology, University of Cambridge, NHS Blood and Transplant Site, Cambridge, UK
- 2Department of Obstetrics-Gynecology, Western Visayas Medical Center, Iloilo City, Philippines
- 3Diagnostics for the Real World (Europe) Ltd, Cambridge Science Park, Cambridge, UK
- Dr H H Lee, Diagnostics Development Unit, Department of Haematology, University of Cambridge, NHS Blood and Transplant Site, Cambridge CB2 2PT, UK; hl207{at}cam.ac.uk
- Accepted 19 April 2009
- Published Online First 26 April 2009
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: 1.3×102 to 1.4×107 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.
Footnotes
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Funding: The study was funded by a grant from The Wellcome Trust (081371/Z/06/Z).
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Competing interests: C-EM, LMM-T and HHL are equity holders of Diagnostics for the Real World Ltd, a spin-off company based on rapid test technologies developed at the University of Cambridge. The University of Cambridge and The Wellcome Trust are also equity holders of the company.
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Ethics approval: Ethics approval was provided by the Institutional Research Ethics Committee of the Western Visayas Medical Center.
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Patient consent: Obtained.
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Contributors: C-EM organised study materials, took part in writing and editing the paper and supervised NAAT assays on matched specimens. FGS was the clinical site coordinator, collected specimens, performed HandiLab-C testing on-site and organised shipment of specimens from the Philippines to Cambridge. HJ performed blinded NAAT assays on matched specimens. LMM-T helped in the design and implementation of the study, was the overall study coordinator and took primary responsibility for writing the initial draft of the manuscript. HHL was the principal investigator of the project, conceptualised the study and contributed to writing and editing the paper.
