The SELFCHECK® Prostate Health Test is an in-vitro diagnostic self-testing kit for the detection of raised levels of prostate specific antigen (PSA) in a capillary whole blood sample. Self-testing is meant only as a preliminary check of physiological biomarker levels, and is not a substitute for a professional medical diagnosis. A positive or negative result does not definitively indicate the presence or absence of a medical condition and should always be followed up with a confirmatory test by a doctor or healthcare professional.
As part of the CE certification process according to the in-vitro diagnostics directive (IVDD) for a self-testing device and subsequent registration with MHRA, the manufacturer (VEDALAB, France) performed structured layperson usability trials and demonstrated that the test provided reliable results in the hands of laypersons. This information was evaluated independently by a Notified Body before certification was approved.
In this separate, independent evaluation of a total of 11,278 tests sold by SELFCHECK, the usability of the PSA self-test by laypersons in the UK was evaluated by recording the number of complaints received as a percentage of tests reviewed. No complaints were excluded from the analysis. Although the demographics of the customer were unknown, due to the nature of the biomarker measured in the test, it was assumed that the end user would be male, and likely to be aged around 50 years or older. The clinical efficiency for the diagnosis of prostate cancer or any other prostate related medical condition was not part of this evaluation.
Method
SELFCHECK self-test kits were purchased by the end-user, either from a retailer or directly from the distributor's website (selfcheckmedical.com). The instructions for use (IFU) leaflet provided with each test kit clearly informs the user to contact the SELFCHECK customer care team if they do not get a result or have any problems using the test. As each test costs the user around £20, it was expected that the customer would contact SELFCHECK for further help and advice if they had any problems.
Results
Out of 11,278 tests, the total number of test failures reported to the company by the end user due to an issue with using the test was 28 (0.248%). The user was asked to send a photo of the test cassette, lot number and any other relevant information so that the cause of the issue could be identified.
Issues reported by the user
Problems using the lancing device (2)
Collecting the blood drop with the pipette (14)
Invalid result (12)
Reasons for an invalid result
Insufficient blood (4)
Not adding enough chase buffer (1)
Blood clotting in the sample well (2)
Unidentified cause (5)
Discussion
The most common reason for an inconclusive result was not collecting and applying sufficient blood to the test cassette. Two single-use lancets were provided with each test kit to allow the user to have a second attempt to obtain sufficient blood. The lancets supplied with the test kit were manufactured by UK medical device company Owen Mumford (Unistik 3 Extra) and are known for their high reliability and use in the NHS.
The percentage of failures was likely to be higher than reported, as some of the tests sold may not have been used, some users may not have reported a failure, and others may not have been aware that their test has failed. However, the IFU supplied with the test provides clear diagrams of what a positive, negative and inconclusive test result should look like, and included contact information for the SELFCHECK customer care team in the UK for help if needed.
The combination of components and IFU provided with the SELFCHECK test were unique to the SELFCHECK brand and the results should not be interpreted as a guide to the performance of other brands or variations of PSA self-test kits.
Summary
The SELFCHECK Prostate Health Test had a low user failure rate of 0.248% when used by laypersons. The main reason for failure were issues with collecting the blood sample (0.151%). The company provided telephone and online access to a UK based customer care team to help the end-user understand how the test works and to provide guidance to ensure the customer could get a result.