A finger-prick test that provides CD4 cell count results within an average of 30 minutes is as accurate as laboratory-based testing and highly acceptable to patients, UK investigators report in Sexually Transmitted Infections.
Doctors at the Mortimer Market Clinic in central London assessed the performance and acceptability of the PIMA point-of-care CD4 test in 254 patients between 2010 and 2011.
“We found that the POCT [point-of-care test] was particularly useful in the newly diagnosed patients, both for practical reasons of clinical assessment and management, but also in terms of patient experience,” comment the authors.
CD4 cell monitoring is an essential component of routine HIV care and is used to monitor disease progression as well as guiding decisions about the use of antiretroviral therapy and prophylactic treatment for infections.
In the UK, testing is performed in a laboratory. This can be inconvenient for patients as it may require a return visit to the clinic to obtain the results. Delays in the availability of test results can also mean that necessary treatments are also delayed.
However, results can be more promptly delivered using point-of-care CD4 tests. These were developed for resource-limited settings, where there is limited access to laboratory services. A number of studies suggest that their results are well correlated with traditional laboratory assessment of CD4 cell count.
There is little information about the use of point-of-care testing in richer countries.
Investigators therefore designed a study evaluating the performance and acceptability of this type of test.
Their study population included 254 patients who received care between December 2010 and July 2011. People with chronic HIV infection as well as people newly diagnosed with HIV were recruited to the study. Point-of-care testing was also assessed in people attending the emergency 'walk-in' service.
Most of the participants were men (87%) and their median age was 41 years. Laboratory testing showed that their median CD4 cell count was 450 cells/mm3.
There was a strong correlation between the results of the point-of-care tests and laboratory CD4 cell counts (p < 0.001).
However, in 201 participants, the point-of-care test gave a lower CD4 cell count than the laboratory tests. This has been noted in other research. The investigators do not believe that this would lead to worse care, but caution that it could cause people unnecessary anxiety.
The investigators showed that results of the point-of-care test could be trusted to guide decisions about the use of antiretroviral therapy and prophylaxis against infections.
Using laboratory tests as the 'gold standard', the investigators found that for CD4 cell counts below 200 cells/mm3, the point-of-care test had a sensitivity of 93% and a specificity of 96%. For a CD4 cell count of 350 cells/mm3, the test had a sensitivity of 95% and a specificity of 88%.
Results of point-of-care testing were available within a median of 30 minutes. The maximum waiting time was 45 minutes.
The rapid availability of results was especially useful for people who were newly diagnosed. A total of nine participants were symptomatic and seven of these had a CD4 cell count below 350 cells/mm3. Two people were started on PCP prophylaxis and one person started HIV therapy within a week.
In all, 54% of the study participants expressed a preference for point-of-care testing. The majority (87%) said they would be happy to wait 20 minutes for their results. Just under half indicated that point-of-care testing at GPs would be acceptable if available.
“The role of POCT in the UK needs further evaluation but may find a place in outreach services of the future as well as in the routine clinic setting in providing immediate CD4 results,” suggest the authors.
They conclude, “we have shown that accurate results with an immediate point-of-care CD4 test can offer a more comprehensive, patient friendly one-stop assessment of patients and is particularly valuable to those newly diagnosed with HIV infection.”
Herbert S et al. Evaluation of PIMA point-of-care CD4 testing in a large UK HIV service. Sex Transm Infect, doi: 10.1136/sextrans-2012-050507, 2012.