Comparison of a new, affordable flow cytometric method and the manual magnetic bead technique for CD4 T-lymphocyte counting in a northern Nigerian setting

Rapid In Vitro Assessment of Antimicrobial Drug Effect Bridging Clinically Relevant Pharmacokinetics: A Comprehensive Methodology

Rapid in vitro assessment of antimicrobial drug efficacy under clinically relevant pharmacokinetic conditions is an essential element of both drug development and clinical use. Here, we present a comprehensive overview of a recently developed novel integrated methodology for rapid assessment of such efficacy, particularly against the emergence of resistant bacterial strains, as jointly researched by the authors in recent years. This methodology enables rapid in vitro assessment of the antimicrobial efficacy of single or multiple drugs in combination, following clinically relevant pharmacokinetics. The proposed methodology entails (a) the automated collection of longitudinal time-kill data in an optical-density instrument; (b) the processing of collected time-kill data with the aid of a mathematical model to determine optimal dosing regimens under clinically relevant pharmacokinetics for single or multiple drugs; and (c) in vitro validation of promising dosing regimens in a hollow fiber system. Proof-of-concept of this methodology through a number of in vitro studies is discussed. Future directions for the refinement of optimal data collection and processing are discussed.

Economic burden of congenital athymia in the United States for patients receiving supportive care during the first 3 years of life

AIMS

Congenital athymia is an ultra-rare pediatric condition characterized by the lack of thymus in utero and the naïve T cells critical for infection defense and immune regulation. Patients with congenital athymia receive supportive care to minimize and treat infections, autoimmune phenomena, and autologous graft-versus-host disease (aGVHD) manifestations, but historically, die within the first 3 years of life with supportive care only. We estimated the healthcare resource utilization and economic burden of supportive care over patients' first 3 years of life in the United States.

METHODS

A medical chart audit by the treating physician was used to collect patient data from birth to age 3 on clinical manifestations associated with congenital athymia (clinical manifestations due to underlying syndromic conditions excluded). Using costs and charges from publicly available sources, the total economic burden of direct medical costs and charges for the first 3 years of life (considered "lifetime" for patients receiving supportive care) and differences in economic burden between patients with higher and lower inpatient hospitalization durations were estimated.

RESULTS

All patients (n = 10) experienced frequent infections and aGVHD manifestations; 40% experienced ≥1 episode of sepsis, and 20% had recurrent sepsis episodes annually. The estimated mean 3-year economic burden per patient was US$5,534,121 (2020 US dollars). The annual mean inpatient hospitalization duration was 150.6 days. Inpatient room charges accounted for 79% of the economic burden, reflecting the high costs of specialized care settings required to prevent infection, including isolation. Patients with high inpatient utilization (n = 5; annual mean inpatient hospitalization duration, 289.6 days) had an estimated 3-year economic burden of US$9,926,229.

LIMITATIONS

The total economic burden may not be adequately represented due to underestimation of some direct costs or overestimation of others.

CONCLUSIONS

Current treatment of patients with congenital athymia (supportive care) presents a high economic burden to the healthcare system.

Rapid and cost-effective evaluation of bacterial viability using fluorescence spectroscopy

A rapid and easy method that takes advantage of an inexpensive and portable fibre-based spectroscopic system (optrode) to determine the ratio of live to dead bacteria is proposed. Mixtures of live and dead Escherichia coli with proportions of live:dead cells varying from 0 to 100% were stained using SYTO 9 and propidium iodide (PI) and measured using the optrode. We demonstrated several approaches to obtaining the proportions of live:dead E. coli in a mixture of both live and dead, from analyses of the fluorescence spectra collected by the optrode. To find a suitable technique for predicting the percentage of live bacteria in a sample, four analysis methods were assessed and compared: SYTO 9:PI fluorescence intensity ratio, an adjusted fluorescence intensity ratio, single-spectrum support vector regression (SVR) and multi-spectra SVR. Of the four analysis methods, multi-spectra SVR obtained the most reliable results and was able to predict the percentage of live bacteria in 10⁸ bacteria/mL samples between c. 7 and 100% live, and in 10⁷ bacteria/mL samples between c. 7 and 73% live. By demonstrating the use of multi-spectra SVR and the optrode to monitor E. coli viability, we raise points of consideration for spectroscopic analysis of SYTO 9 and PI and aim to lay the foundation for future work that uses similar methods for different bacterial species.

Near real-time enumeration of live and dead bacteria using a fibre-based spectroscopic device

A rapid, cost-effective and easy method that allows on-site determination of the concentration of live and dead bacterial cells using a fibre-based spectroscopic device (the optrode system) is proposed and demonstrated. Identification of live and dead bacteria was achieved by using the commercially available dyes SYTO 9 and propidium iodide, and fluorescence spectra were measured by the optrode. Three spectral processing methods were evaluated for their effectiveness in predicting the original bacterial concentration in the samples: principal components regression (PCR), partial least squares regression (PLSR) and support vector regression (SVR). Without any sample pre-concentration, PCR achieved the most reliable results. It was able to quantify live bacteria from 108 down to 106.2 bacteria/mL and showed the potential to detect as low as 105.7 bacteria/mL. Meanwhile, enumeration of dead bacteria using PCR was achieved between 108 and 107 bacteria/mL. The general procedures described in this article can be applied or modified for the enumeration of bacteria within populations stained with fluorescent dyes. The optrode is a promising device for the enumeration of live and dead bacterial populations particularly where rapid, on-site measurement and analysis is required.

CD4 enumeration technologies: a systematic review of test performance for determining eligibility for antiretroviral therapy

Background

Measurement of CD4⁺ T-lymphocytes (CD4) is a crucial parameter in the management of HIV patients, particularly in determining eligibility to initiate antiretroviral treatment (ART). A number of technologies exist for CD4 enumeration, with considerable variation in cost, complexity, and operational requirements. We conducted a systematic review of the performance of technologies for CD4 enumeration.

Methods and Findings

Studies were identified by searching electronic databases MEDLINE and EMBASE using a pre-defined search strategy. Data on test accuracy and precision included bias and limits of agreement with a reference standard, and misclassification probabilities around CD4 thresholds of 200 and 350 cells/μl over a clinically relevant range. The secondary outcome measure was test imprecision, expressed as % coefficient of variation. Thirty-two studies evaluating 15 CD4 technologies were included, of which less than half presented data on bias and misclassification compared to the same reference technology. At CD4 counts <350 cells/μl, bias ranged from -35.2 to +13.1 cells/μl while at counts >350 cells/μl, bias ranged from -70.7 to +47 cells/μl, compared to the BD FACSCount as a reference technology. Misclassification around the threshold of 350 cells/μl ranged from 1-29% for upward classification, resulting in under-treatment, and 7-68% for downward classification resulting in overtreatment. Less than half of these studies reported within laboratory precision or reproducibility of the CD4 values obtained.

Conclusions

A wide range of bias and percent misclassification around treatment thresholds were reported on the CD4 enumeration technologies included in this review, with few studies reporting assay precision. The lack of standardised methodology on test evaluation, including the use of different reference standards, is a barrier to assessing relative assay performance and could hinder the introduction of new point-of-care assays in countries where they are most needed.

Fast sorting of CD4+ T cells from whole blood using glass microbubbles

The isolation of CD4 positive T lymphocyte (CD4+) from peripheral blood is important for monitoring patients after HIV infection. Here, we demonstrate a fast isolation strategy for CD4+ cells that involves mixing blood and glass microbubbles. After the specific binding of target cells to the microbubbles carrying specific antibodies on their surface, target cells will spontaneously float to the top of the blood vial and can be quickly separated. Using this strategy, we demonstrate that the isolation of CD4+ cells in less than 5 minutes and with better than 90% efficiency. This strategy for cell isolation based on buoyancy and glass microbubbles is quick and inexpensive, minimizes blood handling, does not require magnetic fields, or centrifugation equipment, and could lead to new, efficient strategies for AIDS diagnosis in resource-limited areas.

Predictions of CD4 lymphocytes' count in HIV patients from complete blood count

Background

HIV diagnosis, prognostic and treatment requires T CD4 lymphocytes’ number from flow cytometry, an expensive technique often not available to people in developing countries. The aim of this work is to apply a previous developed methodology that predicts T CD4 lymphocytes’ value based on total white blood cell (WBC) count and lymphocytes count applying sets theory, from information taken from the Complete Blood Count (CBC).

Methods

Sets theory was used to classify into groups named A, B, C and D the number of leucocytes/mm³, lymphocytes/mm³, and CD4/μL³ subpopulation per flow cytometry of 800 HIV diagnosed patients. Union between sets A and C, and B and D were assessed, and intersection between both unions was described in order to establish the belonging percentage to these sets. Results were classified into eight ranges taken by 1000 leucocytes/mm³, calculating the belonging percentage of each range with respect to the whole sample.

Results

Intersection (A ∪ C) ∩ (B ∪ D) showed an effectiveness in the prediction of 81.44% for the range between 4000 and 4999 leukocytes, 91.89% for the range between 3000 and 3999, and 100% for the range below 3000.

Conclusions

Usefulness and clinical applicability of a methodology based on sets theory were confirmed to predict the T CD4 lymphocytes’ value, beginning with WBC and lymphocytes’ count from CBC. This methodology is new, objective, and has lower costs than the flow cytometry which is currently considered as Gold Standard.

Evaluation of CD4+ T cells in HIV patients presenting with malaria at the University of Ilorin Teaching Hospital Nigeria

CD4 count is an important immunological marker of disease progression in HIV seropositive patients. This study was carried out to determine the effect of malaria or fever of unknown origin on the population of CD4+ T lymphocytes of HIV seropositive patients attending the highly active antiretroviral therapy (HAART) clinic of the University of Ilorin Teaching Hospital, Ilorin, Nigeria. 36 subjects were selected for this study. Ongoing history of fever was used as a case definition for malaria and malaria was confirmed from microscopic examination of thick and thin film of blood sample obtained from the patients during presentation with fever. The CD4 count was evaluated during presentation of fever and post-fever using flow cytometry. There was significant decrease in CD4 count of the patients. However, upon classifying the patients into 2 groups - those that returned to the clinic after a week and those that returned after a month; a significant increase in CD4 count was noticed in the group that returned after a week, while a significant decrease was noticed in the group that returned after a month (at p value of 95 %). Further classification of the patients based on presence of malaria parasite, and body temperature resulted in varying effects on CD4 count post-fever (in the general group, 27 were positive for malaria parasites). Of these 27, there was an increase in CD4 count in 9 (33.3 %). However in the group that returned after a week, all 6 (100 %) that were positive for malaria parasites showed increase in CD4 count. Five (26.3 %) of the 19 patients that had body temperature within the range of 35.5-37.4 °C showed an increase in CD4 count, while 7 (41.2 %) of the 17 patients that had body temperature of 37.5 °C and above showed an increase in CD4 count. The results led to the conclusion that while some components of the immune response to malaria could strengthen the immune system of HIV seropositive patients by increasing their CD4 count, other components will suppress their immunity by decreasing their CD4 count, accelerating the progression to AIDS.

Research needs and challenges in the development of HIV diagnostic and treatment monitoring tests for use in resource-limited settings

PURPOSE OF REVIEW

The aim of this article is to review research priorities for current and new technologies to diagnose HIV and to monitor treatment response, including technologies to enumerate CD4 cell counts and quantify plasma viral load, in resource-limited settings.

RECENT FINDINGS

Numerous challenges remain before HIV diagnostic and treatment monitoring technologies can be broadly implemented, especially in rural areas. New technologies that are less costly and complex to use are in development and may be better suited than current technologies for use in resource-limited settings. Investment into research activities is needed for development, evaluation and validation of new technologies. The lack of clarity in the process for evaluation and validation for these technologies affects country and program-level decisions on the appropriateness of technologies for individual settings. Implementation research is needed to assess how best to use CD4 and viral load to guide initiation and management of antiretroviral treatment, as well as how best to scale up diagnosis of HIV serostatus in infants. Studies also need to be conducted to determine if the same CD4 cutoffs can be used in resource-limited settings for initiating antiretroviral therapy and prophylaxis against opportunistic infections due to potential regional differences and the impact of other common co-morbidities on CD4 cell counts.

SUMMARY

Increased availability of antiretroviral therapy in resource-limited settings increases the need for reliable, less costly and simpler to use HIV diagnostic and treatment monitoring technologies. Global leadership is needed to coordinate the research and development necessary to ensure that HIV diagnostic and treatment monitoring technologies are properly evaluated in the setting where they will be used.

Clinical applications and availability of CD4+ T cell count testing in sub-Saharan Africa

The absolute CD4+ T cell count in adults and CD4+ T cell percentage of lymphocytes (CD4%) in pediatrics compliment clinical history and physical examination to inform decisions about initiating antiretroviral therapy (ART). In addition, these immunologic markers predict host susceptibility to specific opportunistic infections, selected drug toxicities, and mortality. These benefits argue strongly for the availability of CD4+ T cell testing capacity in all settings where HIV infection is treated. Several currently available flow cytometry-based devices, and novel CD4+ T cell enumeration techniques such as the panleucogating CD4 are especially suitable for resource-constrained settings. At this time, unfortunately, the landscape of HIV care in sub-Saharan Africa is a mosaic characterized by large areas where CD4+ T cell testing capacity is limited or unavailable, and small, but growing, pockets where the capacity exists. Routine HIV quantification is currently unaffordable and unsustainable in the great majority of the region; therefore, a reliance on CD4+ T cell testing is inevitable for now. To this end, correcting the disparities in CD4+ T cell testing capacity and defining the minimum laboratory requirements for the safe use of antiretroviral drugs through well-designed clinical studies are some of the most urgent priorities of the ongoing global scale-up of ART.

Evaluation of the Partec flow cytometer against the BD FACSCalibur system for monitoring immune responses of human immunodeficiency virus-infected patients in Zimbabwe

A single-platform volumetric flow cytometer, the Partec Cyflow SL_3, was evaluated against a BD FACSCalibur/Sysmex XT1800i dual platform for measuring CD4(+) lymphocytes, total lymphocytes, and the percentage of CD4 lymphocytes in whole-blood samples for monitoring the immune systems of human immunodeficiency virus (HIV)/AIDS patients. Statistical analyses for precision, correlation, and agreement were performed. Coefficients of variation (CV) of 5.8, 4.6, and 3.9% were obtained for low, medium, and high CD4(+) cell counts, respectively, using the SL_3, and CV of 3.7, 4.0, and 0.94 were obtained for the same categories, using the BD FACSCalibur. Significant correlations (P < 0.005) between the two assays for CD4 counts, total lymphocyte counts, and percentages of CD4 were obtained, with correlation coefficients of 0.99, 0.96, and 0.99, respectively (n = 229). Using the Bland-Altman plot, mean biases of -18 cell/microl (95% confidence interval (CI); -91 to 54 cells/microl), -0.8% (95% CI; -3.6 to 2%), and -36.8 cells/microl (95% CI; -477 to 404 cells/microl) were obtained for comparisons of CD4 counts, percentages of CD4 cells, and total lymphocyte counts, respectively. The effects of the age of the samples on the three parameters were also analyzed by comparing results from the same samples analyzed at 6, 24, and 48 h after collection. The correlation coefficients for comparisons among different time points for the same machine and among all the time points for the two different machines were greater than 0.90. These data showed that the Partec Cyflow SL_3 assay is comparable to the BD FACSCalibur/Sysmex XT1800i dual-platform method for measuring the amount of CD4(+) cells and total lymphocytes and the percentages of CD4 cells in blood samples for the purpose of monitoring HIV/AIDS patients.

Effective evaluation of novel low-cost CD4 monitoring assays

Indian generic pharmaceutical manufacturers have dramatically reduced the price of antiretroviral therapy thus improving access, but monitoring costs of the patients on therapy remain high. Few low-cost monitoring assays are available and validation against gold standard is exceedingly important before implementation. Validity is defined as the degree to which the results of the new technique correspond to the true state of the phenomena being measured by the gold standard. Majority of publications report validation of low-cost CD4 assay using correlation coefficient, which is the best measure of association, and a few publications report intra-class correlation coefficient, which is a measure of reliability. However, Bland-Altman analysis that directly quantifies the difference seen between the novel low-cost CD4 assay and the gold standard is the most ideal approach. Absolute CD4 counts estimated for samples collected from 110 HIV+ and 118 HIV- individuals using novel EasyCD4 assay and the gold standard FACSCount assay were validated using correlation coefficient, intra-class correlation coefficient and Bland Altman analysis. The results from these different analyses have been compared and the significance of each has been explained. Hence, to validate a low-cost assay Bland-Altman analysis and plot is recommended.

Affordable flow cytometry for enumeration of absolute CD4+ T-lymphocytes to identify subtype C HIV-1 infected adults requiring antiretroviral therapy (ART) and monitoring response to ART in a resource-limited setting

BACKGROUND

The World Health Organization (WHO)'s "3 x 5 program" has spurred efforts to place 3 million people on combination antiretroviral therapy (ART) for treatment of AIDS in resource-limited countries. Paradoxically, the cost of CD4+ T-lymphocyte count essential for decision-making to commence HIV positive adults on ART as well as for monitoring responses to ART remains unaffordable in most resource-limited countries. Thus, low-cost methods for enumerating CD4+ T-lymphocyte are urgently needed.

OBJECTIVE

To evaluate Cyflow cytometry (Cyflow SL, Partec, Munster, Germany) for enumeration of absolute CD4+ T-lymphocyte in subtype C HIV-1 seropositive subjects using FACSCount (Becton and Dickinson, Immunocytometry Systems, San Jose, CA, USA) as the "predicate method".

METHODS

A total of 150 HIV-1 seropositive subjects were included in the evaluation exercise. Fifty-eight specimens were collected from pregnant HIV-1 seropositive women (subtype C drug resistance study). Twenty-seven specimens were collected from women and their spouses with AIDS followed in a Duke ART study to assess the immunologic and virologic responses to generic ART, comprising Stavudine, Lamivudine and Nevirapine (Stalanev, Varichem Labs, Harare, Zimbabwe). Sixty-five specimens were collected from AIDS patients enrolled in an ongoing Kaposi Sarcoma (KS) study to investigate impact of ART on KS progression. Enumeration of CD4+ T-lymphocytes using FACSCount is routinely conducted for all the three studies. The Medical Research Council of Zimbabwe and Medicines Control Authority of Zimbabwe approved the studies. Whole blood was collected in EDTA vacutainer tubes and aliquoted into two tubes (200 microL in each). CD4+ T-lymphocyte counts were enumerated using a Cyflow counter, in the Department of Immunology and a FACSCount in the Department of Obstetrics and Gynaecology within 6 hours of phlebotomy following manufacturers' instructions.

RESULTS

Using linear regression analysis, there was a very strong correlation (R = 0.991) between the overall CD4+ T-lymphocyte counts obtained by FACSCount and those obtained by Cyflow. When data analysis was stratified by study groups, there was a strong correlation between the FACSCount and Cyflow CD4+ T-lymphocyte counts from subjects in the three independent studies; Subtype C resistance (R2 = 0.987), Duke ART (R2 = 0.980) and KS (R2 = 0.994), Table 1. Using Bland-Altman plots, the overall, absolute CD4+ T lymphocytes obtained by the two methods were in excellent agreement (mean difference 1.21, 95% Confidence Interval {CI): -2.1 to 3.3). For the 0-250 CD4+ T-lymphocytes range, the CD4 counts obtained using FACSCount were also in good agreement with those obtained using Cyflow counter (mean difference = 2.6 cells/microL, 95% CI: -1.1 to 6.3). Similarly, in the 251-500 (mean difference 1.0, cells/microL, 95% CI: -3.7 to 5.6) and the 501-1200 (mean difference = 0.29 cells/microL, 95% CI: -8.1 to 8.7) CD4 T-lymphocytes range, good agreement was observed.

CONCLUSION

The Cyflow counter is as accurate as the FACSCount in enumerating absolute CD4+ T-lymphocytes in the range 1-1200 cells/muL. Cyflow cytometry is relatively affordable, easy to use technology that is useful not only in identifying HIV seropositive individuals who require ART but also for monitoring immunologic responses to ART.

Absolute CD4 T-Cell Counting in Resource-Poor Settings

Flow cytometry is an accurate but expensive method to determine absolute CD4 cell counts. We compared different methods to measure absolute CD4 counts in blood samples from HIV-infected and uninfected subjects using a research/clinical flow cytometer (FACScan); a dedicated clinical instrument (FACSCount); and a volumetric, mobile, open-system flow cytometer equipped with 3 fluorescence and 2 light scatter detectors (Cyflow SL blue). The FACScan and Cyflow were used as single-platform instruments, but they differ in running cost, which is a central factor for resource-poor settings. Direct volumetric and bead-based CD4 measurements on the Cyflow were compared with 2 bead-based single-platform CD4 measurements on the FACSCount and on FACScan (TruCount) in "Le Dantec" Hospital, Dakar, Senegal, using whole blood samples from 102 HIV+ and 28 HIV- subjects. The agreement between the various measurement methods was evaluated by Bland-Altman analysis. Volumetric CD4 measurements on the Cyflow using a no-lyse-no-wash (NLNW) procedure and a lyse-no-wash (LNW) procedure correlated well with each other (R2 = 0.98) and with CD4 measurements on the FACSCount (R2 = 0.97) and FACScan (R2 = 0.97), respectively. Red blood cell lysis had no negative effect on the accuracy of absolute CD4 counting on the Cyflow. An excellent correlation was observed between bead-based CD4 measurements on the Cyflow and CD4 measurements on the FACSCount (R2 = 0.99) and FACScan (R2 = 0.99). Rigid internal and external quality control monitoring and adequate training of technicians were considered essential to generate accurate volumetric CD4 measurements on the Cyflow.