Laboratory-based performance evaluation of PIMA CD4+ T-lymphocyte count point-of-care by lay-counselors in Kenya

Prehospital use of point-of-care tests by community health workers: a scoping review

Introduction

Point-of-Care Tests (POCTs) are utilized daily in resource abundant regions, however, are limited in the global south, particularly in the prehospital setting. Few studies exist on the use of non-malarial POCTs by Community Health Workers (CHWs). The purpose of this scoping review is to delineate the current diversity in and breadth of POCTs evaluated in the prehospital setting.

Methods

A medical subject heading (MeSH) analysis of known key articles was done by an experienced medical librarian and scoping searches were performed in each database to capture "point of care testing" and "community health workers." This review was guided by the PRISMA Extension for scoping reviews.

Results

2735 publications were returned, 185 were nominated for full-text review, and 110 studies were confirmed to meet study criteria. Majority focused on malaria (74/110; 67%) or HIV (25/110; 23%); 9/110 (8%) described other tests administered. Results from this review demonstrate a broad geographic range with significant heterogeneity in terminology for local CHWs.

Conclusion

The use of new POCTs is on the rise and may improve early risk stratification in limited resource settings. Current evidence from decades of malaria POCTs can guide future implementation strategies.

Point of Care Diagnostics in Resource-Limited Settings: A Review of the Present and Future of PoC in Its Most Needed Environment

Point of care (PoC) diagnostics are at the focus of government initiatives, NGOs and fundamental research alike. In high-income countries, the hope is to streamline the diagnostic procedure, minimize costs and make healthcare processes more efficient and faster, which, in some cases, can be more a matter of convenience than necessity. However, in resource-limited settings such as low-income countries, PoC-diagnostics might be the only viable route, when the next laboratory is hours away. Therefore, it is especially important to focus research into novel diagnostics for these countries in order to alleviate suffering due to infectious disease. In this review, the current research describing the use of PoC diagnostics in resource-limited settings and the potential bottlenecks along the value chain that prevent their widespread application is summarized. To this end, we will look at literature that investigates different parts of the value chain, such as fundamental research and market economics, as well as actual use at healthcare providers. We aim to create an integrated picture of potential PoC barriers, from the first start of research at universities to patient treatment in the field. Results from the literature will be discussed with the aim to bring all important steps and aspects together in order to illustrate how effectively PoC is being used in low-income countries. In addition, we discuss what is needed to improve the situation further, in order to use this technology to its fullest advantage and avoid “leaks in the pipeline”, when a promising device fails to take the next step of the valorization pathway and is abandoned.

Preclinical Assessment of a Cartridge-Based Flow-Through Assay for Determination of Adult CD4 T-Cell Count

Background:

Despite the emphasis on viral load testing, current HIV testing guidelines consider CD4 T-cell count measurement as an important criterion for assessing disease progression, making decisions about anti-retroviral therapy regime changes, and treating HIV infected individuals with opportunistic infections. The CD4 counting by established methods (e.g., flow cytometry) presents challenges not only in resource-scarce settings due to cost and lack of skilled technicians but also in resource-rich areas where it is limited to centralized facilities.

Objective:

Current options for Point-Of-Care (POC) CD4 enumeration are few and labor-intensive, prompting the need for newer technological methods that can overcome the aforementioned challenges.

Methods:

The novel and patented flow-through cell counting assay (FTCA) described previously (Bystryak et al., 2019) was developed further into a point-of-care CD4 testing system using a disposable cartridge device and a portable imaging instrument. A pilot study with ~100 samples using this device was conducted to assess the validity of FTCA as a POC test for the measurement of CD4 count.

Results:

The FTCA signal was found to be linear over a wide range (17 - 1540 cells/μL) of CD4 T-cell concentration. The FTCA method also exhibits a strong agreement with flow cytometry, with very low bias (− 7 cells/μL) towards CD4 count measurement.

Conclusion:

The cartridge-based FTCA method has great potential to be a fully quantitative method with low complexity, portability, low-cost, and wide applicability in clinical practice.

Onsite healthcare worker acceptability and performance of the point-of-care Pima CD4 assay in Dar es Salaam, Tanzania

Background: Healthcare workers’ acceptance of and ability to perform point-of-care testing is important for reliable and accurate results. The Alere Pima™ CD4 assay (Pima CD4) is the CD4 point-of-care test for HIV management in Tanzania.Objectives: To evaluate healthcare workers’ acceptance and performance of Pima CD4 testing.Methods: The study was implemented in five high volume sites in Dar es Salaam, Tanzania, in 2011. Trained healthcare workers performed Pima testing using three whole-blood specimens collected from each patient: venous blood, fingerstick blood directly applied to a Pima cartridge (capillary-direct), and fingerstick blood collected in a microtube (capillary-microtube). Using a semi-structured interview guide, we interviewed 11 healthcare workers about specimen collection methods and Pima CD4 acceptability. Quantitative responses were analysed using descriptive statistics. Open-ended responses were summarised by thematic areas. Pima CD4 results were analysed to determine variation between cadres.Results: Healthcare workers found Pima CD4 user-friendly and recommended its use in low volume, peripheral facilities. Both venous and capillary-direct blood were considered easy to collect, with venous preferred. Advantages noted with venous and capillary-microtube methods were the ability to retest, perform multiple tests, or delay testing. Pima CD4 results were trusted by the healthcare workers and were in agreement with laboratory Pima testing.Conclusion: In this point-of-care testing setting, the Pima CD4 assay was accepted by healthcare workers. Both venous and fingerstick capillary blood specimens can be used with Pima CD4, but fingerstick methods may require more intensive training on technique to minimise variation in results and increase acceptability.

A flow-through cell counting assay for point-of-care enumeration of CD4 T-cells

CD4 T-cell count is a priority for staging HIV disease and guiding clinical management as part of HIV care. Conventional CD4 T-cell enumeration methods based on flow cytometry are expensive, require well-trained personnel, and are challenging to use in rural, resource-scarce areas. A simple CD4 T-cell count test that can be used at point-of care, the Flow-Through cell Counting Assay (FTCA), is described in this article. The FTCA is based on the use of: 1) a special membrane that selectively retains white blood cells (WBCs); 2) a sample delivery system; and 3) optical signal detection. To show the feasibility of the FTCA, a proof-of-concept prototype of the FTCA cassette and digital camera or handheld reflectance meter were used for obtaining quantitative assay results within 30 min. The results show that the FTCA allows for quantitative enumeration of CD4 T-cells in the clinically relevant range of CD4 T-cell concentrations. The advantages of the FTCA technology, including simplicity, short analysis time, and portability, suggest that FTCA has great potential for use in clinical practice and wide applicability for other cell-based diagnostic tests.

Performance of non-laboratory staff for diagnostic testing and specimen collection in HIV programs: A systematic review and meta-analysis

BACKGROUND

In most high HIV burden countries, many HIV patients do not have reliable access to required diagnostic laboratory tests. Task shifting of clinical tasks to lower cadres of health care workers and lay counselors has been successful in scaling up treatment for HIV and may also be an effective strategy in expanding access to essential diagnostic testing.

METHODS

We screened major electronic databases between 1 January 2005 to 26 August 2018 to identify studies assessing ease of use and accuracy of task shifting of HIV-related diagnostic testing and/or specimen collection to non-laboratory health staff. Two independent reviewers screened all titles and abstracts for studies that analyzed diagnostic accuracy, patient impact, ease-of-use, or cost-effectiveness. Studies were assessed for quality, bias, and applicability following the QUADAS-2 framework. We generated summary estimates using random-effects meta-analyses.

RESULTS

We identified 42 relevant studies. Overall, point-of-care CD4 testing performed by non-laboratory staff had a mean bias of -54.44 (95% CI: -72.40 --36.48) compared to conventional laboratory-based. Though studies were limited, the diagnostic accuracy of point-of-care alanine transaminase enzyme (ALT) and hemoglobin testing performed by non-laboratory staff was comparable to conventional laboratory-based testing by laboratory professionals. Point-of-care testing and/or specimen collection were generally found to be acceptable and easy to use for non-laboratory staff.

CONCLUSIONS

Task shifting of testing using point-of-care technologies to non-laboratory staff was comparable to laboratory professionals operating the same technology in the laboratory. Some variability was observed comparing the performance of point-of-care CD4 testing by non-laboratory staff to conventional laboratory-based technologies by laboratory professionals indicating potential lower performance was likely technological rather than operator caused. The benefits of task shifting of testing may outweigh any possible harms as task shifting allows for increased decentralization, access of specific diagnostics, and faster result delivery.

Field Performance of PIMA Point-of-Care Machine for CD4 Enumeration Under a Mobile HIV Counseling and Testing Program in Remote Fishing Communities of Lake Victoria, Uganda

Uganda is among the most HIV/AIDS-afflicted countries, and many HIV-infected persons live in remote areas with poor access to health care. The success of HIV care programs relies in part on patient monitoring using CD4 T cell counts. We conducted an evaluation of the point-of-care PIMA test using BD FACSCount as a gold standard. One hundred fifty-one participants were enrolled, provided venous blood and samples tested at the point of care with the Alere PIMA™ CD4 Analyzer and the BD FACSCount in the UVRI-IAVI main laboratory. Correlation between the methods was assessed, as was the ability of the Pima Analyzer to predict values <200, <350, and ≥500 CD4 cells/mm³ when compared with BD FACSCount as the gold standard. A near-perfect positive Pearson correlation coefficient (r = 0.948; p < .0001) between the two methods was observed. The Alere PIMA Analyzer had a mean bias of -32.5 cells/mm³. The sensitivity and specificity, for PIMA to predict CD4 lymphocyte count less than 200 cells/mm³, were 71.4% and 100%, respectively; less than 350 cells/mm³ were 84.6% and 94.6%, respectively; and at CD4 count less than 500 cells/mm³ were 94.4% and 100%. The Alere Pima Analyzer provides reliable CD4 cell count measurement and is suitable for monitoring and screening eligible HIV patients in hard-to-reach settings.

Qualitative assessment of South African healthcare worker perspectives on an instrument-free rapid CD4 test

Background

Accurate measurement of CD4 cell counts remains an important tenet of clinical care for people living with HIV. We assessed an instrument-free point-of-care CD4 test (VISITECT® CD4) based on a lateral flow principle, which gives visual results after 40 min. The test involves five steps and categorises CD4 counts as above or below 350 cells/μL. As one component of a performance evaluation of the test, this qualitative study explored the views of healthcare workers in a large women and children’s hospital on the acceptability and feasibility of the test.

Methods

Perspectives on the VISITECT® CD4 test were elicited through in-depth interviews with eight healthcare workers involved in the performance evaluation at an antenatal care facility in Johannesburg, South Africa. Audio recordings were transcribed in full and analysed thematically.

Results

Healthcare providers recognised the on-going relevance of CD4 testing. All eight perceived the VISITECT® CD4 test to be predominantly user-friendly, although some felt that the need for precision and optimal concentration in performing test procedures made it more challenging to use. The greatest strength of the test was perceived to be its quick turn-around of results. There were mixed views on the semi-quantitative nature of the test results and how best to integrate this test into existing health services. Participants believed that patients in this setting would likely accept the test, given their general familiarity with other point-of-care tests.

Conclusions

Overall, the VISITECT® CD4 test was acceptable to healthcare workers and those interviewed were supportive of scale-up and implementation in other antenatal care settings. Both health workers and patients will need to be oriented to the semi-quantitative nature of the test and how to interpret the results of tests.

Electronic supplementary material

The online version of this article (10.1186/s12913-019-3948-x) contains supplementary material, which is available to authorized users.

Task-shifting of CD4 T cell count monitoring by the touchscreen-based Muse™ Auto CD4/CD4% single-platform system for CD4 T cell numeration: Implication for decentralization in resource-constrained settings

BACKGROUND

The accuracy of CD4 T cell monitoring by the recently developed flow cytometry-based CD4 T cell counting Muse™ Auto CD4/CD4% Assay analyzer (EMD Millipore Corporation, Merck Life Sciences, KGaA, Darmstadt, Germany) was evaluated in trained lay providers against laboratory technicians.

METHODS

After 2 days of training on the Muse™ Auto CD4/CD4% analyzer, EDTA-blood samples from 6 HIV-positive and 4 HIV-negative individuals were used for CD4 T cell counting in triplicate in parallel by 12 trained lay providers as compared to 10 lab technicians.

RESULTS

Mean number of CD4 T cells in absolute number was 829 ± 380 cells/μl by lay providers and 794 ± 409 cells/μl by technicians (P > 0.05); and in percentage 36.2 ± 14.8%CD4 by lay providers and 36.1 ± 15.0%CD4 by laboratory technician (P > 0.05). The unweighted linear regression and Passing-Bablok regression analyses on CD4 T cell results expressed in absolute count revealed moderate correlation between CD4 T cell counts obtained by lay providers and lab technicians. The mean absolute bias measured by Bland-Altman analysis between CD4 T cell/μl obtained by lay providers and lab technicians was -3.41 cells/μl. Intra-assay coefficient of variance (CV) of Muse™ Auto CD4/CD4% in absolute number was 10.1% by lay providers and 8.5% by lab technicians (P > 0.05), and in percentage 5.5% by lay providers and 4.4% by lab technicians (P > 0.05). The inter-assay CV of Muse™ Auto CD4/CD4% in absolute number was 13.4% by lay providers and 10.3% by lab technicians (P > 0.05), and in percentage 7.8% by lay providers and 6.9% by lab technicians (P > 0.05).

CONCLUSIONS

The study demonstrates the feasibility of CD4 T cell counting using the alternative flow cytometer Muse™ Auto CD4/CD4% analyzer by trained lay providers and therefore the practical possibility of decentralization CD4 T cell counting to health community centers.

Effect of point-of-care CD4 cell count results on linkage to care and antiretroviral initiation during a home-based HIV testing campaign: a non-blinded, cluster-randomised trial

BACKGROUND

HIV disease staging with referral laboratory-based CD4 cell count testing is a key barrier to the initiation of antiretroviral treatment (ART). Point-of-care CD4 cell counts can improve linkage to HIV care among people living with HIV, but its effect has not been assessed with a randomised controlled trial in the context of home-based HIV counselling and testing (HBCT).

METHODS

We did a two-arm, cluster-randomised, controlled efficacy trial in two districts of western Kenya with ongoing HBCT. Housing compounds were randomly assigned (1:1) to point-of-care CD4 cell counts (366 compounds with 417 participants) or standard-of-care (318 compounds with 353 participants) CD4 cell counts done at one of three referral laboratories serving the study catchment area. In each compound, we enrolled people with HIV not engaged in care in the previous 6 months. All participants received post-test counselling and referral for HIV care. Point-of-care test participants received additional counselling on the result, including ART eligibility if CD4 was less than 350 cells per μL, the cutoff in Kenyan guidelines. Participants were interviewed 6 months after enrolment to ascertain whether they sought HIV care, verified through chart reviews at 23 local clinics. The prevalence of loss to follow-up at 6 months (LTFU) was listed as the main outcome in the study protocol. We analysed linkage to care at 6 months (defined as 1-LTFU) as the primary outcome. All analyses were by intention to treat. This trial is registered at ClinicalTrials.gov, number NCT02515149.

FINDINGS

We enrolled 770 participants between July 1, 2013, and Feb 28, 2014. 692 (90%) had verified linkage to care status and 78 (10%) were lost to follow-up. Of 371 participants in the point-of-care group, 215 (58%) had linked to care within 6 months versus 108 (34%) of 321 in the standard-of-care group (Cox proportional multivariable hazard ratio [HR] 2·14, 95% CI 1·67-2·74; log rank p<0·0001).

INTERPRETATION

Point-of-care CD4 cell counts in a resource-limited HBCT setting doubled linkage to care and thereby improved ART initiation. Given the substantial economic and logistic hindrances to providing ART for all people with HIV in resource-limited settings in the near term, point of care CD4 cell counts might have a role in prioritising care and improving linkage to care.

FUNDING

US Centers for Disease Control and Prevention.