Farzad Noubary

A Paper-Based Multiplexed Transaminase Test for Low-Cost, Point-of-Care Liver Function Testing

A paper-based, multiplexed microfluidic assay allows rapid, semiquantitative, visual measurement of transaminases in clinical specimens. Spot-On Toxicity Testing “Just a little pinprick,” Pink Floyd once reassured its listeners. Of certainty, they were not singing about liver function tests. Nevertheless, the soothing lyric can be just as readily applied to paper-based microfluidics, for which only a droplet of blood—from a finger pinprick—can indicate whether a patient has liver toxicity and needs additional care. In a new study, Pollock and colleagues developed a cost-effective, multiplexed paper-based test that measures two enzymes in human blood commonly associated with liver injury: aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Levels of these transaminases are elevated in patients with liver toxicity, such as those on several medications at once (for example, drug “cocktails” for HIV and tuberculosis). In the developing world, limited resources often prevent patients from having access to the automated laboratory tests used in developed countries. To address this unmet need, Pollock et al. created a point-of-care (POC) device that requires only blood and the human eye for analysis. The authors stacked layers of patterned paper containing “test zones” with chemistries specific for measuring AST and ALT. When blood (<35 μl) is spotted on the device, it interacts with reagents to provide, in 15 min, a colorimetric readout that falls into one of three “bins”: <3×, 3×-5×, or >5× the upper limit of normal. This semiquantitative, color-coded message, along with three control zones, informs the doctor of basic facts needed to devise the next treatment steps. Pollock and coauthors tested their paper-based device using 233 blood samples with a range of AST and ALT concentrations. Over all three bins, the device was ≥90% accurate with both serum and whole blood when compared to standard measurement techniques. Costing only pennies to make, these devices can be used at POC to inform clinicians of possible liver injury, without the long waits for results to return from centralized laboratories. With readouts obtained in near real time, patients all over the world can be comfortably reassured of their health. In developed nations, monitoring for drug-induced liver injury through serial measurements of serum transaminases [aspartate aminotransferase (AST) and alanine aminotransferase (ALT)] in at-risk individuals is the standard of care. Despite the need, monitoring for drug-related hepatotoxicity in resource-limited settings is often limited by expense and logistics, even for patients at highest risk. This article describes the development and clinical testing of a paper-based, multiplexed microfluidic assay designed for rapid, semiquantitative measurement of AST and ALT in a fingerstick specimen. Using 223 clinical specimens obtained by venipuncture and 10 fingerstick specimens from healthy volunteers, we have shown that our assay can, in 15 min, provide visual measurements of AST and ALT in whole blood or serum, which allow the user to place those values into one of three readout “bins” [<3× upper limit of normal (ULN), 3 to 5× ULN, and >5× ULN, corresponding to tuberculosis/HIV treatment guidelines] with >90% accuracy. These data suggest that the ultimate point-of-care fingerstick device will have high impact on patient care in low-resource settings.

Diagnostic point-of-care tests in resource-limited settings

The aim of diagnostic point-of-care testing is to minimise the time to obtain a test result, thereby allowing clinicians and patients to make a quick clinical decision. Because point-of-care tests are used in resource-limited settings, the benefits need to outweigh the costs. To optimise point-of-care testing in resource-limited settings, diagnostic tests need rigorous assessments focused on relevant clinical outcomes and operational costs, which differ from assessments of conventional diagnostic tests. We reviewed published studies on point-of-care testing in resource-limited settings, and found no clearly defined metric for the clinical usefulness of point-of-care testing. Therefore, we propose a framework for the assessment of point-of-care tests, and suggest and define the term test efficacy to describe the ability of a diagnostic test to support a clinical decision within its operational context. We also propose revised criteria for an ideal diagnostic point-of-care test in resource-limited settings. Through systematic assessments, comparisons between centralised testing and novel point-of-care technologies can be more formalised, and health officials can better establish which point-of-care technologies represent valuable additions to their clinical programmes.

Risk of Progression to Active Tuberculosis Following Reinfection With Mycobacterium tuberculosis

BACKGROUND The risk of progression to active tuberculosis is greatest in the several years following initial infection. The extent to which latent tuberculosis infection reduces the risk of progressive disease following reexposure and reinfection is not known. Indirect estimates from population models have been highly variable. METHODS We reviewed prospective cohort studies of persons exposed to individuals with infectious tuberculosis that were published prior to the widespread treatment of latent tuberculosis to estimate the incidence of tuberculosis among individuals with latent tuberculosis infection (LTBI group) and without latent tuberculosis (uninfected; UI group). We calculated the incidence rate ratio (IRR) of tuberculosis disease following infection between these 2 groups. We then adjusted incidence for expected reactivation, proportion of each group that was infected, and median time of observation following infection during the study. RESULTS We identified 18 publications reporting tuberculosis incidence among 23 paired cohorts of individuals with and without latent infection (total N = 19 886). The weighted mean adjusted incidence rate of tuberculosis in the LTBI and UI groups attributable to reinfection was 13.5 per 1000 person-years (95% confidence interval [CI]: 5.0-26.2 per 1000 person-years) and that attributable to primary infection was 60.1 per 1000 person-years (95% CI: 38.6-87.4 per 1000 person-years). The adjusted IRR for tuberculosis in the LTBI group compared with the UI group was 0.21 (95% CI: .14-.30). CONCLUSIONS Individuals with latent tuberculosis had 79% lower risk of progressive tuberculosis after reinfection than uninfected individuals. The risk reduction estimated in this study is greater than most previous estimates made through population models.

Cost-Effectiveness of HIV Treatment as Prevention in Serodiscordant Couples

BACKGROUND The cost-effectiveness of early antiretroviral therapy (ART) in persons infected with human immunodeficiency virus (HIV) in serodiscordant couples is not known. Using a computer simulation of the progression of HIV infection and data from the HIV Prevention Trials Network 052 study, we projected the cost-effectiveness of early ART for such persons. METHODS For HIV-infected partners in serodiscordant couples in South Africa and India, we compared the early initiation of ART with delayed ART. Five-year and lifetime outcomes included cumulative HIV transmissions, life-years, costs, and cost-effectiveness. We classified early ART as very cost-effective if its incremental cost-effectiveness ratio was less than the annual per capita gross domestic product (GDP;

Linkage to HIV, TB and Non-Communicable Disease Care from a Mobile Testing Unit in Cape Town, South Africa

8,100 in South Africa and

Mobile HIV Screening in Cape Town, South Africa: Clinical Impact, Cost and Cost-Effectiveness

1,500 in India), as cost-effective if the ratio was less than three times the GDP, and as cost-saving if it resulted in a decrease in total costs and an increase in life-years, as compared with delayed ART. RESULTS In South Africa, early ART prevented opportunistic diseases and was cost-saving over a 5-year period; over a lifetime, it was very cost-effective (

Not All Are Lost: Interrupted Laboratory Monitoring, Early Death, and Loss to Follow-Up (LTFU) in a Large South African Treatment Program

590 per life-year saved). In India, early ART was cost-effective (

Routine HIV Testing in Adolescents and Young Adults Presenting to an Outpatient Clinic in Durban, South Africa

1,800 per life-year saved) over a 5-year period and very cost-effective (

Field Evaluation of a Prototype Paper-Based Point-of-Care Fingerstick Transaminase Test

530 per life-year saved) over a lifetime. In both countries, early ART prevented HIV transmission over short periods, but longer survival attenuated this effect; the main driver of life-years saved was a clinical benefit for treated patients. Early ART remained very cost-effective over a lifetime under most modeled assumptions in the two countries. CONCLUSIONS In South Africa, early ART was cost-saving over a 5-year period. In both South Africa and India, early ART was projected to be very cost-effective over a lifetime. With individual, public health, and economic benefits, there is a compelling case for early ART for serodiscordant couples in resource-limited settings. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

Midlife Blood Pressure and Late-Life GFR and Albuminuria: An Elderly General Population Cohort

Background HIV counseling and testing may serve as an entry point for non-communicable disease screening. Objectives To determine the yield of newly-diagnosed HIV, tuberculosis (TB) symptoms, diabetes and hypertension, and to assess CD4 count testing, linkage to care as well as correlates of linkage and barriers to care from a mobile testing unit. Methods A mobile unit provided screening for HIV, TB symptoms, diabetes and hypertension in Cape Town, South Africa between March 2010 and September 2011. The yield of newly-diagnosed cases of these conditions was measured and clients were followed-up between January and November 2011 to assess linkage. Linkage to care was defined as accessing care within one, three or six months post-HIV diagnosis (dependent on CD4 count) and one month post-diagnosis for other conditions. Clinical and socio-demographic correlates of linkage to care were evaluated using Poisson regression and barriers to care were determined. Results Of 9,806 clients screened, the yield of new diagnoses was: HIV (5.5%), TB suspects (10.1%), diabetes (0.8%) and hypertension (58.1%). Linkage to care for HIV-infected clients, TB suspects, diabetics and hypertensives was: 51.3%, 56.7%, 74.1% and 50.0%. Only disclosure of HIV-positive status to family members or partners (RR=2.6, 95% CI: 1.04-6.3, p=0.04) was independently associated with linkage to HIV care. The main barrier to care reported by all groups was lack of time to access a clinic. Conclusion Screening for HIV, TB symptoms and hypertension at mobile units in South Africa has a high yield but inadequate linkage. After-hours and weekend clinics may overcome a major barrier to accessing care.