This page outlines the in-house laboratory services provided by Preventx Limited.
The Preventx Laboratory is a UKAS accredited testing laboratory, No. 7568.
Where laboratory diagnostic services are provided in whole, or as a part of a product of service offered by Preventx Limited, they are done so in accordance with a Quality System adhering to international standards. This document summarises key areas of this system that relate to the laboratory services offered to clients.
The Preventx Laboratory is located in The Sheffield Bioincubator, which occupies a prime location on the western edge of the Sheffield city centre. The location provides excellent transport and distribution links for sample receipt. The secure 1,000 sq. ft. suite contains both modern office space and a Category 2 wet laboratory for the exclusive use of Preventx Limited.
The Preventx Laboratory is currently able to offer the following assays:
Where other assays are provided by Preventx Limited to support products and services, the samples may be referred to sub-contracted laboratories. Samples referred for testing that include assays other than those above, fall outside the scope of Preventx’s Quality System (and this document) and are offered in accordance with Quality System of the referral laboratory.
The laboratory carries out testing on the Roche Cobas 4800® System. The Cobas provides fully automated sample preparation with real-time polymerase chain reaction (PCR) based NAAT technology for amplification and detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG). Single (CT) and dual (CTNG) testing services are available.
Where necessary, samples may be referred to a subcontracted laboratory using the same assays (for example, in order to provide a backup in the case of equipment failure in the Preventx Laboratory). Please note that samples will always be tested in a laboratory accredited to national or international standards (ISO17025, CPA or HPA accepted equivalent).
Where samples are referred to an alternate laboratory, this will be noted on the specimen record and is fully traceable. For more information about referral laboratories, or details of the testing path for a specific specimen, contact lab@preventx.com.
All samples received into the laboratory are stabilised and prepared for testing as soon as possible after receipt (usually within 5 hours). In instances where timely stabilisation is not possible, samples are refrigerated (between 2-8°C) until preparation can be carried out.
A study carried out by Preventx has shown that samples transported though the Royal Mail and remaining un-refrigerated up to 14 days still produce accurate test results. Any samples the laboratory believe to have not been refrigerated or stabilised within 12-14 days of collection are still tested (as positive results would likely still be detected) however negative outcomes are handled as ‘out-of-protocol’ as it is believed that the negative result has a slightly increased probability of being false. There are however, very few samples to which this outcome is applied (only a small number of samples during heavy postal periods, such as the winter festive season).
Once prepared into Roche PCR Media samples are handled, tested and stored according to manufacturer guidelines. Samples are then queued to be tested in-house or referred to be tested at an alternate laboratory. Preventx endeavour to test at least 90% of samples within 5 working days of receipt; however the majority of samples are usually tested within 48 hours.
Where available, raw samples received by Preventx are retained until a result is submitted for the sample. Stabilised samples for all tests are retained for a minimum of 7 days, during which they may be re-tested by request at the Preventx Laboratory or an external laboratory if a third-party confirmation is required.
Forms received with samples are retained for a minimum of 1 month, and in some cases may be stored electronically and attached to the samples specimen record in the Preventx Specimen Management system.
Platform accuracy as stated and validated by manufacturer:
Research carried out by Roche Diagnostics (Overview over sensitivity and specificity evaluation studies of the cobas® 4800 CT Test) further evaluated sensitivity and specificity for the Chlamydia assay with a range of sample types and produced the following results for male urine, female urine and self-taken vaginal swabs in asymptomatic patients:
Similar sensitivity was observed with symptomatic patients, ranging from -0.5% to +3.6% when compared to the above values.
The platforms Positive Predictive Value (PPV) and Negative Predictive Value (NPV) can be calculated based on the prevalence among patients testing. While Preventx monitor PPV and NPV using live prevalence data, the following table shows the hypothetical PPV and NPV attained for a given prevalence (and based on Roche’s overall sensitivity and specificity values).
Where prevalence drops and the estimated PPV falls below 90%, confirmatory testing will be carried out on all positive samples.
Where tested on site in the Preventx Laboratory or referred to an external laboratory, all samples are tested in a laboratory accredited to national or international standards (ISO17025, CPA or HPA approved equivalent).
Preventx follow the relevant standards (and endeavour to follow future revisions) recommended in the ‘Standards for the management of sexually transmitted infections (STIs)’, as published by the British Society for Sexual Health and HIV (BASHH).
Preventx has completed the NHS Information Governance Toolkit scoring of over 90% (with most requirements attaining Level 3, and all attaining level 2 or higher). All patient information is collected, stored and processed securely.
The testing algorithm used for testing samples is based on the HPA’s UK Standards for Microbiology Investigations and BASHH guidelines with adjustments for dual (CT & NG) testing and platform manufacturer test methods.
Where samples are unable to be tested (for example, there was no sample provided, or the kit was not completed correctly) an ‘out of protocol’ result will be submitted. In cases where not enough sample is present for repeat testing, the ‘Invalid’ test result outcome will be followed and an ‘Equivocal’ result will be submitted.
Where CT and NG are both detected, multiple test flow routes are followed (i.e. ensuring each submitted result has completed its respective process as per above). Estimated PPV values are evaluated based on regular analysis of overall testing positivity.
All test results are submitted to the client or provider via a ‘simplified’ method, in that no hard copy result details are issued.
All test results are stored by Preventx Limited in a secure central database however the result delivery channels may vary based on client agreements. In most cases, results are available via the Preventx Specimen Management system.
While the result outcome and associated data will always be clearly available, the web-based result and sample management systems are continually under development and improvement, so the presentation of results may evolve over time.
The Preventx Laboratory submits all CTAD data to the HPA on a quarterly basis.
While individual agreements with clients may apply variations to the services offered (and take precedence over the service specification outlined in this document), there are two primary types of service offered by Preventx that include bespoke laboratory testing. Service variations specific to these types of service are outlined below.
Where agreed with clients (or where historically in place) Preventx will provide notifications to patients upon results being released (for example, by text message).
Unless otherwise agreed, positive patients will be contacted with the message “Hi {First Name}, the results for your test ({Specimen Code}) are now available, please call {NHS Provider Number} to collect your results as soon as you can.” and negative patients will be contacted with the message “Hi {First Name}, you'll be glad to know your test ({Specimen Code}) came back all clear! See freetest.me for more details.”. Where a patient sample can’t be tested they are asked to submit a new sample by requesting a new test kit.
Single (CT) and dual (CTNG) testing services are both available via freetest.me and are carried out as agreed with the client (or as per historic service configuration).
Where the freetest.me service has been commissioned it is required that a satisfactory care pathway is put in place for all patients that use the service via the respective region. There are also a number of key responsibilities which must be agreed in order to offer an ethical remote screening service, please see below.
Where private testing patients order tests from test.me, they will be tested in the Preventx Laboratory where the booked tests are for CT or CTNG exclusively. Where other tests are also included, samples are referred to an external laboratory.
Other private and commercial screening services may be offered and in such cases the service offered will be clearly documented and agreed with the client(s).
Test results for test.me customers will be available via the online test tracking service. Notifications that results are available may be sent via text message and email; however test results are only issued via the specimen tracking system.
Private patients are requested to read and show acceptance of their responsibilities when ordering sexual health tests.
It is important for patients to acknowledge that they must manage their results, and take control of their own personal health. This includes seeking treatment for any positive results and notifying current and past partners of their potential infection, where appropriate. Where available, signposting is provided for treatment services local to the patient.
Preventx will be responsible for:
The client or provider, where appropriate, will be responsible for: