Comparison of point-of-care versus laboratory-based CD4 cell enumeration in HIV-positive pregnant women

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.

Toward Improving Accessibility of Point-of-Care Diagnostic Services for Maternal and Child Health in Low- and Middle-Income Countries

Point-of-care (POC) testing can improve health care provision in settings with limited access to health care services. Access to POC diagnostic services has shown potential to alleviate some diagnostic challenges and delays associated with laboratory-based methods in low- and middle-income countries. Improving accessibility to POC testing (POCT) services during antenatal and perinatal care is among the global health priorities to improve maternal and child health. This review provides insights on the availability of POC testing designed for diagnosing HIV, syphilis, and malaria in pregnancy to improve maternal and child health. In addition, factors such as accessibility of POC testing, training of health work force, and the efficiency of POC testing services delivery in low- and middle-income countries are discussed. A framework to help increase access to POC diagnostic services and improve maternal and child health outcomes in low- and middle-income countries is proposed.

CD4 cell count variability with repeat testing in South Africa: Should reporting include both absolute counts and ranges of plausible values?

Although eligibility for antiretroviral treatment is no longer based on CD4 thresholds, CD4 testing remains important. Variation in CD4 cell count complicates initiation of antibiotic prophylaxis, differential diagnoses and assessments of immunological recovery. Five hundred and fifty-three HIV-positive antiretroviral-naïve adults, recruited from inner-city clinics, had three serial CD4 cell count tests. Test 1 was mostly done in a laboratory network supporting primary care clinics, while Tests 2 and 3 were performed in a tertiary-level laboratory. Reproducibility was assessed through Bland-Altman limits of agreement and coefficients of variation. Participants, a mean age of 34 years and mostly female (57%), had a median 203 CD4 cells/μL (Test 1). Seventeen per cent classified as having advanced HIV disease (CD4 cell count  < 200 cells/µL) on Test 1 had a CD4 cell count > 200 cells/µL on Tests 2 and 3. Mean differences between tests were <10 cells/µL for all comparisons. Limits of agreement for Tests 1 and 2 were -106.9 to 112.7 and coefficient of variation 15. Corresponding figures for Tests 2 and 3 were -88.2 to 103.4, and 13. Means of tests were similar, suggesting no systematic measurement differences, despite testing being done at different times. Variations were, however, considerable in many instances, though smaller in testing done in the same laboratory. CD4 cut-offs must not be applied rigidly, but rather constitute one amongst many factors used to guide patient care. Moreover, given the difficulties in determining whether CD4 changes are due to HIV disease, or other biological and laboratory factors, CD4 laboratory reports should include a range of plausible values, not only the absolute count.

Performance of point-of-care CD4 testing technologies in resource-constrained settings: a systematic review and meta-analysis

Background

Point-of-care (POC) CD4 testing increases patient accessibility to assessment of antiretroviral therapy eligibility. This review evaluates field performance in low and middle-income countries (LMICs) of currently available POC CD4 technologies.

Methods

Eight electronic databases were searched for field studies published between January 2005 and January 2015 of six POC CD4 platforms: PointCare NOW™, Alere Pima™ CD4, Daktari™ CD4 Counter, CyFlow® CD4 miniPOC, BD FACSPresto™, and MyT4™ CD4. Due to limited data availability, meta-analysis was conducted only for diagnostic performance of Pima at a threshold of 350 cells/μl, applying a bivariate multi-level random-effects modelling approach. A covariate extended model was also explored to test for difference in diagnostic performance between capillary and venous blood.

Results

Twenty seven studies were included. Published field study results were found for three of the six POC CD4 tests, 24 of which used Pima. For Pima, test failure rates varied from 2 to 23 % across study settings. Pooled sensitivity and specificity were 0.92 (95 % CI = 0.88–0.95) and 0.87 (95 % CI = 0.85–0.88) respectively. Diagnostic performance by blood sample type (venous vs. capillary) revealed non-significant differences in sensitivity (0.94 vs 0.89) and specificity (0.86 vs 0.87), respectively in the extended model (Wald χ²(2) = 4.77, p = 0.09).

Conclusions

POC CD4 testing can provides reliable results for making treatment decision under field conditions in low-resource settings. The Pima test shows a good diagnostic performance at CD4 cut-off of 350 cells/μl. More data are required to evaluate performance of POC CD4 testing using venous versus capillary blood in LMICs which might otherwise influence clinical practice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1931-2) contains supplementary material, which is available to authorized users.

HIV viraemia and mother-to-child transmission risk after antiretroviral therapy initiation in pregnancy in Cape Town, South Africa

OBJECTIVES

Maternal HIV viral load (VL) drives mother-to-child HIV transmission (MTCT) risk but there are few data from sub-Saharan Africa, where most MTCT occurs. We investigated VL changes during pregnancy and MTCT following antiretroviral therapy (ART) initiation in Cape Town, South Africa.

METHODS

We conducted a prospective study of HIV-infected women initiating ART within routine antenatal services in a primary care setting. VL measurements were taken before ART initiation and up to three more times within 7 days postpartum. Analyses examined VL changes over time, viral suppression (VS) at delivery, and early MTCT based on polymerase chain reaction (PCR) testing up to 8 weeks of age.

RESULTS

A total of 620 ART-eligible HIV-infected pregnant women initiated ART, with 2425 VL measurements by delivery (median gestation at initiation, 20 weeks; median pre-ART VL, 4.0 log₁₀ HIV-1 RNA copies/mL; median time on ART before delivery, 118 days). At delivery, 91% and 73% of women had VL ≤ 1000 and ≤ 50 copies/mL, respectively. VS was strongly predicted by time on therapy and pre-ART VL. The risk of early MTCT was strongly associated with delivery VL, with risks of 0.25, 2.0 and 8.5% among women with VL < 50, 50-1000 and > 1000 copies/mL at delivery, respectively (P < 0.001).

CONCLUSIONS

High rates of VS at delivery and low rates of MTCT can be achieved in a routine care setting in sub-Saharan Africa, indicating the effectiveness of currently recommended ART regimens. Women initiating ART late in pregnancy and with high VL appear substantially less likely to achieve VS and require targeted research and programmatic attention.

PIMA™ point-of-care testing for CD4 counts in predicting antiretroviral initiation in HIV-infected individuals in KwaZulu-Natal, Durban, South Africa

Introduction

Limited information is available on the usefulness of the PIMA™ analyser in predicting antiretroviral treatment eligibility and outcome in a primary healthcare clinic setting in disadvantaged communities in KwaZulu-Natal, South Africa.

Materials and methods

The study was conducted under the eThekwini Health Unit, Durban, KwaZulu-Natal. Comparison of the enumeration of CD4+ T-cells in 268 patients using the PIMA™ analyser and the predicate National Health Laboratory Services (NHLS) was undertaken during January to July 2013. Bland-Altman analysis to calculate bias and limits of agreement, precision and levels of clinical misclassification at various CD4+ T-cell count thresholds was performed.

Results

There was high precision of the PIMA™ control bead cartridges with low and normal CD4+ T-cell counts using three different PIMA™ analysers (%CV < 5). Under World Health Organization (WHO) guidelines (≤ 500 cells/mm³), the sensitivity of the PIMA™ analyser was 94%, specificity 78% and positive predictive value (PPV) 95%. There were 24 (9%) misclassifications, of which 13 were false-negative in whom the mean bias was 149 CD4+ T-cells/mm³. Most (87%) patients returned for their CD4 test result but only 67% (110/164) of those eligible (≤ 350 cells/mm³) were initiated on antiretroviral therapy (ART) with a time to treatment of 49 days (interquartile range [IQR], 42–64 days).

Conclusion

There was adequate agreement between PIMA™ analyser and predicate NHLS CD4+ T-cell count enumeration (≤ 500 cells/mm³) in adult HIV-positive individuals. The high PPV, sensitivity and acceptable specificity of the PIMA™ analyser technology lend it as a reliable tool in predicting eligibility and rapid linkage to care in ART programmes.

Performance Evaluation of the Becton Dickinson FACSPresto™ Near-Patient CD4 Instrument in a Laboratory and Typical Field Clinic Setting in South Africa

Background

The BD-FACSPresto^™ CD4 is a new, point-of-care (POC) instrument utilising finger-stick capillary blood sampling. This study evaluated its performance against predicate CD4 testing in South Africa.

Methods

Phase-I testing: HIV+ patient samples (n = 214) were analysed on the Presto^™ under ideal laboratory conditions using venous blood. During Phase-II, 135 patients were capillary-bled for CD4 testing on FACSPresto^™, performed according to manufacturer instruction. Comparative statistical analyses against predicate PLG/CD4 method and industry standards were done using GraphPad Prism 6. It included Bland-Altman with 95% limits of agreement (LOA) and percentage similarity with coefficient of variation (%CV) analyses for absolute CD4 count (cells/μl) and CD4 percentage of lymphocytes (CD4%).

Results

In Phase-I, 179/217 samples yielded reportable results with Presto^™ using venous blood filled cartridges. Compared to predicate, a mean bias of 40.4±45.8 (LOA of -49.2 to 130.2) and %similarity (%CV) of 106.1%±7.75 (7.3%) was noted for CD4 absolute counts. In Phase-2 field study, 118/135 capillary-bled Presto^™ samples resulted CD4 parameters. Compared to predicate, a mean bias of 50.2±92.8 (LOA of -131.7 to 232) with %similarity (%CV) 105%±10.8 (10.3%), and 2.87±2.7 (LOA of -8.2 to 2.5) with similarity of 94.7±6.5% (6.83%) noted for absolute CD4 and CD4% respectively. No significant clinical differences were indicated for either parameter using two sampling methods.

Conclusion

The Presto^™ produced remarkable precision to predicate methods, irrespective of venous or capillary blood sampling. A consistent, clinically insignificant over-estimation (5–7%) of counts against PLG/CD4 and equivalency to FACSCount^™ was noted. Further field studies are awaited to confirm longer-term use.

Evaluation of PIMATM CD4 System for Decentralization of Immunological Monitoring of HIV-Infected Patients in Senegal

BACKGROUND

HIV infection is a concern in the army troupes because of the risk behaviour of the military population. In order to allow regular access to CD4+ T cell enumeration of military personnel as well as their dependents and civilians living with HIV, the Senegalese Army AIDS program is implementing PIMATM Alere technology in urban and semi-urban military medical centres. Validation such device is therefore required prior their wide implementation. The purpose of this study was to compare CD4+ T cell count measurements between the PIMATM Alere to the BD FACSCountTM.

METHODOLOGY

We selected a total of 200 subjects including 50 patients with CD4+ T-cells below 200/mm3, 50 between 200 and 350/mm3, 50 between 351 and 500/mm3, and 50 above 500/mm3. CD4+ T-cell count was performed on venous blood using the BD FASCountTM as reference method and the PIMATM Point of Care technology. The mean biases and limits of agreement between the PIMATM Alere and BD FACSCountTM were assessed with the Bland-Altman analysis, the linear regression performed using the Passing-Bablok regression analysis, and the percent similarity calculated using the Scott method.

RESULTS

Our data have shown a mean difference of 22.3 cells/mm3 [95%CI:9.1-35.5] between the BD FACSCountTM and PIMATM Alere CD4 measurements. However, the mean differences of the two methods was not significantly different to zero when CD4+ T-cell count was below 350/mm3 (P = 0.76). The Passing-Bablok regression in categorized CD4 counts has also showed concordance correlation coefficient of 0.89 for CD4+ T cell counts below 350/mm3 whilst it was 0.5 when CD4 was above 350/mm3.

CONCLUSION

Overall, our data have shown that for low CD4 counts, the results from the PIMATM Alere provided accurate CD4+ T cell counts with a good agreement compared to the FACSCountTM.

CD4 results with a bias larger than hundred cells per microliter can have a significant impact on the clinical decision during treatment initiation of HIV patients

BACKGROUND

CD4 counts are currently used to assess HIV patients for treatment eligibility and to monitor antiretroviral response to treatment. The emerging point-of-care devices could fill an important gap in resource-limited settings. However, the accuracy of CD4-counting instruments is diverse and data on how CD4 measurement errors have an impact on clinical decisions are lacking.

METHODS

Clinicians were queried on the use of CD4 results in their clinical setting. Subsequently, the effect of CD4 measurement errors on treatment initiation was put in a statistical model. Based on clinical CD4 databases from Belgium, Cambodia, and Senegal, the percentage of unchanged clinical decisions was calculated (treatment initiation should start within a 3-month delay [one visit]) for escalating CD4 measurement errors, taking into account the strict or preventive application of CD4 thresholds at 350 or 500 cells/µl used by clinicians.

RESULTS

To ensure that the treatment was initiated appropriately for at least 95% of patients, an error of 5 - 10 cells/µl was allowed. This is significantly smaller than the bias of ±50 cells/µl most clinicians considered acceptable. For limits of agreement (LOA, 1.96 x error) of 100 cells/µl, corresponding to most CD4 instrument evaluations, the misclassification rate of patients was found to be 3 - 28% at the threshold of 350 cells/µl (strict or flexible), and 13 - 20% at 500 cells/µl.

CONCLUSIONS

The maximum allowed CD4 bias on results from new CD4 technologies should not exceed 50 cells/µl (LOA 100 cells/µl) when applied for treatment initiation, to ensure at least 72% of correct clinical decisions. © 2016 International Clinical Cytometry Society.

Implementation and Operational Research: Decentralization Does Not Assure Optimal Delivery of PMTCT and HIV-Exposed Infant Services in a Low Prevalence Setting

BACKGROUND

The consequences of decentralizing prevention of mother-to-child HIV transmission and HIV-exposed infant services to antenatal care (ANC)/labor and delivery (L&D) sites from dedicated HIV care and treatment (C&T) centers remain unknown, particularly in low prevalence settings.

METHODS

In a cohort of mother-infant pairs, we compared delivery of routine services at ANC/L&D and C&T facilities in Kinshasa, Democratic Republic of Congo from 2010-2013, using methods accounting for competing risks (eg, death). Women could opt to receive interventions at 90 decentralized ANC/L&D sites, or 2 affiliated C&T centers. Additionally, we assessed decentralization's population-level impacts by comparing proportions of women and infants receiving interventions before (2009-2010) and after (2011-2013) decentralization.

RESULTS

Among newly HIV-diagnosed women (N = 1482), the 14-week cumulative incidence of receiving the package of CD4 testing and zidovudine or antiretroviral therapy was less at ANC/L&D [66%; 95% confidence interval (CI): 63% to 69%] than at C&T (88%; 95% CI: 83% to 92%) sites (subdistribution hazard ratio, 0.62; 95% CI: 0.55 to 0.69). Delivery of cotrimoxazole and DNA polymerase chain reaction testing to HIV-exposed infants (N = 1182) was inferior at ANC/L&D sites (subdistribution hazard ratio, 0.84; 95% CI: 0.76 to 0.92); the 10-month cumulative incidence of the package at ANC/L&D sites was 89% (95% CI: 82% to 93%) versus 97% (95% CI: 93% to 99%) at C&T centers. Receipt of the pregnancy (20% of 1518, to 64% of 1405) and infant (16%-31%) packages improved post decentralization.

CONCLUSIONS

Services were delivered less efficiently at ANC/L&D sites than C&T centers. Although access improved with decentralization, its potential cannot be realized without sufficient and sustained support.

Errors generated by a point-of-care CD4+ T-lymphocyte analyser: a retrospective observational study in nine countries

OBJECTIVE

To estimate the proportion of invalid results generated by a CD4+ T-lymphocyte analyser used by Médecins Sans Frontières (MSF) in field projects and identify factors associated with invalid results.

METHODS

We collated 25,616 CD4+ T-lymphocyte test results from 39 sites in nine countries for the years 2011 to 2013. Information about the setting, user, training, sampling technique and device repair history were obtained by questionnaire. The analyser performs a series of checks to ensure that all steps of the analysis are completed successfully; if not, an invalid result is reported. We calculated the proportion of invalid results by device and by operator. Regression analyses were used to investigate factors associated with invalid results.

FINDINGS

There were 3354 invalid test results (13.1%) across 39 sites, for 58 Alere PimaTM devices and 180 operators. The median proportion of errors per device and operator was 12.7% (interquartile range, IQR: 10.3-19.9) and 12.1% (IQR: 7.1-19.2), respectively. The proportion of invalid results varied widely by country, setting, user and device. Errors were not associated with settings, user experience or the number of users per device. Tests performed on capillary blood samples were significantly less likely to generate errors compared to venous whole blood.

CONCLUSION

The Alere Pima CD4+ analyser generated a high proportion of invalid test results, across different countries, settings and users. Most error codes could be attributed to the operator, but the exact causes proved difficult to identify. Invalid results need to be factored into the implementation and operational costs of routine CD4+ T-lymphocyte testing.

A meta-analysis of the performance of the Pima™ CD4 for point of care testing

BACKGROUND

The Alere point-of-care (POC) Pima™ CD4 analyzer allows for decentralized testing and expansion to testing antiretroviral therapy (ART) eligibility. A consortium conducted a pooled multi-data technical performance analysis of the Pima CD4.

METHODS

Primary data (11,803 paired observations) comprised 22 independent studies between 2009-2012 from the Caribbean, Asia, Sub-Saharan Africa, USA and Europe, using 6 laboratory-based reference technologies. Data were analyzed as categorical (including binary) and numerical (absolute) observations using a bivariate and/or univariate random effects model when appropriate.

RESULTS

At a median reference CD4 of 383 cells/μl the mean Pima CD4 bias is -23 cells/μl (average bias across all CD4 ranges is 10 % for venous and 15% for capillary testing). Sensitivity of the Pima CD4 is 93% (95% confidence interval [CI] 91.4% - 94.9%) at 350 cells/μl and 96% (CI 95.2% - 96.9%) at 500 cells/μl, with no significant difference between venous and capillary testing. Sensitivity reduced to 86% (CI 82% - 89%) at 100 cells/μl (for Cryptococcal antigen (CrAg) screening), with a significant difference between venous (88%, CI: 85% - 91%) and capillary (79%, CI: 73% - 84%) testing. Total CD4 misclassification is 2.3% cases at 100 cells/μl, 11.0% at 350 cells/μl and 9.5 % at 500 cells/μl, due to higher false positive rates which resulted in more patients identified for treatment. This increased by 1.2%, 2.8% and 1.8%, respectively, for capillary testing. There was no difference in Pima CD4 misclassification between the meta-analysis data and a population subset of HIV+ ART naïve individuals, nor in misclassification among operator cadres. The Pima CD4 was most similar to Beckman Coulter PanLeucogated CD4, Becton Dickinson FACSCalibur and FACSCount, and less similar to Partec CyFlow reference technologies.

CONCLUSIONS

The Pima CD4 may be recommended using venous-derived specimens for screening (100 cells/μl) for reflex CrAg screening and for HIV ART eligibility at 350 cells/μl and 500 cells/μl thresholds using both capillary and venous derived specimens. These meta-analysis findings add to the knowledge of acceptance criteria of the Pima CD4 and future POC tests, but implementation and impact will require full costing analysis.

Field Evaluation of a Point-of-Care CD4 Analyzer for Monitoring HIV Patients in the Interior of the Amazon Region, Brazil

Objective

To evaluate the accuracy of the PIMA point-of-care CD4 analyzer (PIMA) under field conditions in comparison to the current CD4 count system (FACSCalibur), and to evaluate the operational suitability and acceptability of health professionals (HP) and HIV-patients in using the PIMA in health clinics in the Amazon Region.

Methods

CD4 counts were measured onsite by the PIMA using fingerprick blood and in the reference laboratory by both the PIMA and FACSCalibur using venous blood. We used the Bland–Altman method to estimate the mean bias, and calculated the sensitivity and specificity at <200 and <500 cell/μL thresholds. Patients (n = 404) and HP (n = 7) were interviewed on the acceptability and operational suitability of the PIMA.

Results

Using fingerprick blood (n = 337), the PIMA showed a concordance correlation coefficient (Rc) of 0.81, mean difference of -111.9 cell/μL, 93.1%/98.5% sensitivity, and 89.2%/56.7% specificity at <200 and <500 cell/μL thresholds, respectively. Venous blood (n = 340) showed an Rc of 0.89, mean difference of -83.4 cell/μL, 98.3%/97.5% sensitivity, and 93.9%/66.0% specificity at <200 and <500 cell/μL thresholds, respectively. The capillary PIMA was well accepted and found operationally appropriate by patients and HP.

Conclusions

The agreement between both instruments was poor and the PIMA underestimated CD4 cell counts, which was more pronounced at CD4 counts ≥500 cell/μl. The PIMA’s performance with fingerprick blood was less reliable than its performance with venous blood. In Brazil, where antiretroviral treatment is initiated regardless of CD4 counts, the PIMA’s systematic bias towards CD4 underestimation may limit its role for monitoring HIV-patients.

Factors influencing CD4 cell count in HIV-positive pregnant women in a secondary health center in Lagos, Nigeria

Background

Immunity in pregnancy is physiologically compromised, and this may affect CD4 count levels. It is well-established that several factors affect CD4 count level in pregnancy. This study aimed to determine the mean and reference range of CD4 count in human immunodeficiency virus (HIV)-positive pregnant women in Lagos, Nigeria.

Methods

A retrospective study was carried out at antenatal clinics of the Maternal and Child Center of a secondary health center in Lagos State, Nigeria. Records of HIV-positive pregnant women at various gestational ages, including CD4+ cell count at booking, packed cell volume (PCV) at booking and labor, gestational age at delivery, and infant weight and sex were retrieved. The descriptive data was given as mean ± standard deviation (SD). Pearson’s chi-squared test and correlation were used for analytical assessment.

Results

Data were retrieved for a total of 143 patients. The mean age was 31.15±3.78 years. The mean PCV was 31.01%±3.79% at booking and 30.49%±4.80% during labor. The mean CD4 count was 413.87±212.09 cells/μL, with a range of 40 to 1,252 cells/μL. The mean infant weight was 3.05±0.45 kg, with a range of 2 to 5 kg. Age of the mother, gestational age, and PCV at booking were not statistically significantly associated with CD4 count.

Conclusion

Maternal age, gestational age, and PCV at booking had no significant effects on CD4+ cell count levels in pregnancy. The mean CD4+ cell count of HIV-positive pregnant women in Lagos is 413.87±212.09 cells/μL.

Point-of-care CD4 testing to inform selection of antiretroviral medications in south african antenatal clinics: a cost-effectiveness analysis

BACKGROUND

Many prevention of mother-to-child HIV transmission (PMTCT) programs currently prioritize antiretroviral therapy (ART) for women with advanced HIV. Point-of-care (POC) CD4 assays may expedite the selection of three-drug ART instead of zidovudine, but are costlier than traditional laboratory assays.

METHODS

We used validated models of HIV infection to simulate pregnant, HIV-infected women (mean age 26 years, gestational age 26 weeks) in a general antenatal clinic in South Africa, and their infants. We examined two strategies for CD4 testing after HIV diagnosis: laboratory (test rate: 96%, result-return rate: 87%, cost: $14) and POC (test rate: 99%, result-return rate: 95%, cost: $26). We modeled South African PMTCT guidelines during the study period (WHO "Option A"): antenatal zidovudine (CD4 ≤350/μL) or ART (CD4>350/μL). Outcomes included MTCT risk at weaning (age 6 months), maternal and pediatric life expectancy (LE), maternal and pediatric lifetime healthcare costs (2013 USD), and cost-effectiveness ($/life-year saved).

RESULTS

In the base case, laboratory led to projected MTCT risks of 5.7%, undiscounted pediatric LE of 53.2 years, and undiscounted PMTCT plus pediatric lifetime costs of $1,070/infant. POC led to lower modeled MTCT risk (5.3%), greater pediatric LE (53.4 years) and lower PMTCT plus pediatric lifetime costs ($1,040/infant). Maternal outcomes following laboratory were similar to POC (LE: 21.2 years; lifetime costs: $23,860/person). Compared to laboratory, POC improved clinical outcomes and reduced healthcare costs.

CONCLUSIONS

In antenatal clinics implementing Option A, the higher initial cost of a one-time POC CD4 assay will be offset by cost-savings from prevention of pediatric HIV infection.

Evolution of antiretroviral therapy services for HIV-infected pregnant women in Cape Town, South Africa

BACKGROUND

Approaches to antiretroviral therapy (ART) in HIV-infected pregnant women have changed considerably in recent years, but there are few comparative data on the implementation of different models of service delivery.

METHODS

Using routine clinic records we examined ART initiation in pregnant women attending a large antenatal care (ANC) facility between January 2010 and December 2013 in Cape Town, South Africa. Over this time six different service delivery models were implemented sequentially to provide ART in pregnancy, including the integration of ART into ANC, use of point-of-care CD4 cell count testing, and universal ART initiation for all HIV-infected pregnant women.

RESULTS

During the study period 19,432 women sought ANC, levels of HIV testing were high (98%) and 30% of pregnant women tested HIV-positive. Integration of ART into ANC was associated with significant increases in the proportion of eligible women initiating treatment before delivery compared to referral to a separate ART clinic (p<0.001). When CD4 cell counts were used to determine ART eligibility, point-of-care testing was associated with decreased delays to ART initiation compared to laboratory-based testing (p<0.001). The strategy of universal ART led to the highest levels of ART initiation (with 92% of women starting before delivery) and the shortest delays, with 82% of women starting ART on the day of the first ANC visit.

CONCLUSION

Developments in service delivery models, most notably service integration and universal ART for pregnant women, have improved antenatal ART initiation dramatically in this setting. Further research is needed into how strategies for antenatal ART initiation impact maternal and child health over the long-term.

WHO multicenter evaluation of FACSCount CD4 and Pima CD4 T-cell count systems: instrument performance and misclassification of HIV-infected patients

BACKGROUND

CD4⁺ T-cell counts are used to screen and follow-up HIV-infected patients during treatment. As part of the World Health Organization prequalification program of diagnostics, we conducted an independent multicenter evaluation of the FACSCount CD4 and the Pima CD4, using the FACSCalibur as reference method.

METHODS

A total of 440 paired capillary and venous blood samples were collected from HIV-infected patients attending the HIV outpatient clinic in Antwerp, Belgium, and the HIV care and treatment center in Dar es Salam, Tanzania. Capillary blood was run on Pima analyzer, whereas venous blood was analyzed on FACSCount, Pima, and FACSCalibur instruments. Precision and agreement between methods were assessed.

RESULTS

The FACSCount CD4 results were in agreement with the FACSCalibur results with relative bias of 0.4% and 3.1% on absolute CD4 counts and an absolute bias of -0.6% and -1.1% on CD4% in Antwerp and Dar es Salam, respectively. The Pima CD4 results were in agreement with the FACSCalibur results with relative bias of -4.1% and -9.4% using venous blood and of -9.5% and -0.9% using capillary blood in Antwerp and Dar es Salam, respectively. At the threshold of 350 cells per microliter, the FACSCount CD4 and Pima CD4 using venous and capillary blood misclassified 7%, 9%, and 13% of patients, respectively.

CONCLUSIONS

The FACSCount CD4 provides reliable CD4 counts and CD4% and is suitable for monitoring adult and pediatric HIV patients in moderate-volume settings. The Pima CD4 is more suitable for screening eligible adult HIV patients for antiretroviral treatment initiation in low-volume laboratories.

Existing and Emerging Technologies for Point-of-Care Testing

The volume of point-of-care testing (PoCT) has steadily increased over the 40 or so years since its widespread introduction. That growth is likely to continue, driven by changes in healthcare delivery which are aimed at delivering less costly care closer to the patient's home. In the developing world there is the challenge of more effective care for infectious diseases and PoCT may play a much greater role here in the future. PoCT technologies can be split into two categories, but in both, testing is generally performed by technologies first devised more than two decades ago. These technologies have undoubtedly been refined and improved to deliver easier-to-use devices with incremental improvements in analytical performance. Of the two major categories the first is small handheld devices, providing qualitative or quantitative determination of an increasing range of analytes. The dominant technologies here are glucose biosensor strips and lateral flow strips using immobilised antibodies to determine a range of parameters including cardiac markers and infectious pathogens. The second category of devices are larger, often bench-top devices which are essentially laboratory instruments which have been reduced in both size and complexity. These include critical care analysers and, more recently, small haematology and immunology analysers. New emerging devices include those that are utilising molecular techniques such as PCR to provide infectious disease testing in a sufficiently small device to be used at the point of care. This area is likely to grow with many devices being developed and likely to reach the commercial market in the next few years.

Point of care diagnostics for sexually transmitted infections: perspectives and advances

Accurate and inexpensive point-of-care (POC) tests are urgently needed to control sexually transmitted infection epidemics, so that patients can receive immediate diagnoses and treatment. Current POC assays for Chlamydia trachomatis and Neisseria gonorrhoeae perform inadequately and require better assays. Diagnostics for Trichomonas vaginalis rely on wet preparation, with some notable advances. Serological POC assays for syphilis can impact resource-poor settings, with many assays available, but only one available in the U.S. HIV POC diagnostics demonstrate the best performance, with excellent assays available. There is a rapid assay for HSV lesion detection; but no POC serological assays are available. Despite the inadequacy of POC assays for treatable bacterial infections, application of technological advances offers the promise of advancing POC diagnostics for all sexually transmitted infections.