Browsing by Author "Sharp, Alana"
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Item Cost effectiveness of medical devices to diagnose pre-eclampsia in low-resource settings(Elsevier, 2017-07-03) McLaren, Zoe; Sharp, Alana; Hessburg, John P.; Sarvestani, Amir Sabet; Parker, Ethan; Akazili, James; Johnson, Timothy R.B.; Sienko, Kathleen H.Background Maternal mortality remains a major health challenge facing developing countries, with pre-eclampsia accounting for up to 17% of maternal deaths. Diagnosis requires skilled health providers and devices that are appropriate for low-resource settings. This study presents the first cost-effectiveness analysis of multiple medical devices used to diagnose pre-eclampsia in low- and middle-income countries (LMICs). Methods Blood pressure and proteinuria measurement devices, identified from compendia for LMICs, were included. We developed a decision tree framework to assess the cost-effectiveness of each device using parameter values that reflect the general standard of care based on a survey of relevant literature and expert opinion. We examined the sensitivity of our results using one-way and second-order probabilistic multivariate analyses. Results Because the disability-adjusted life years (DALYs) averted for each device were very similar, the results were influenced by the per-use cost ranking. The most cost-effective device combination was a semi-automatic blood pressure measurement device and visually read urine strip test with the lowest combined per-use cost of $0.2004 and an incremental cost effectiveness ratio of $93.6 per DALY gained relative to a baseline with no access to diagnostic devices. When access to treatment is limited, it is more cost-effective to improve access to treatment than to increase testing rates or diagnostic device sensitivity. Conclusions Our findings were not sensitive to changes in device sensitivity, however they were sensitive to changes in the testing rate and treatment rate. Furthermore, our results suggest that simple devices are more cost-effective than complex devices. The results underscore the desirability of two design features for LMICs: ease of use and accuracy without calibration. Our findings have important implications for policy makers, health economists, health care providers and engineers.Item A Data-Driven Evaluation of the Stop TB Global Partnership Strategy of Targeting Key Populations at Greater Risk for Tuberculosis(PLOS, 2016-10-12) McLaren, Zoe; Schnippel, Kathryn; Sharp, AlanaObjective Identifying those infected with tuberculosis (TB) is an important component of any strategy for reducing TB transmission and population prevalence. The Stop TB Global Partnership recently launched an initiative with a focus on key populations at greater risk for TB infection or poor clinical outcomes, due to housing and working conditions, incarceration, low household income, malnutrition, co-morbidities, exposure to tobacco and silica dust, or barriers to accessing medical care. To achieve operational targets, the global health community needs effective, low cost, and large-scale strategies for identifying key populations. Using South Africa as a test case, we assess the feasibility and effectiveness of targeting active case finding to populations with TB risk factors identified from regularly collected sources of data. Our approach is applicable to all countries with TB testing and census data. It allows countries to tailor their outreach activities to the particular risk factors of greatest significance in their national context. Methods We use a national database of TB test results to estimate municipality-level TB infection prevalence, and link it to Census data to measure population risk factors for TB including rates of urban households, informal settlements, household income, unemployment, and mobile phone ownership. To examine the relationship between TB prevalence and risk factors, we perform linear regression analysis and plot the set of population characteristics against TB prevalence and TB testing rate by municipality. We overlay lines of best fit and smoothed curves of best fit from locally weighted scatter plot smoothing. Findings Higher TB prevalence is statistically significantly associated with more urban municipalities (slope coefficient β₁ = 0.129, p < 0.0001, R² = 0.133), lower mobile phone access (β₁ = -0.053, p < 0.001, R² = 0.089), lower unemployment rates (β₁ = -0.020, p = 0.003, R² = 0.048), and a lower proportion of low-income households (β₁ = -0.048, p < 0.0001, R² = 0.084). Municipalities with more low-income households also have marginally higher TB testing rates, however, this association is not statistically significant (β₁ = -0.025, p = 0.676, R² = 0.001). There is no relationship between TB prevalence and the proportion of informal settlement households (β₁ = 0.021, p = 0.136, R² = 0.014). Conclusions These analyses reveal that the set of characteristics identified by the Global Plan as defining key populations do not adequately predict populations with high TB burden. For example, we find that higher TB prevalence is correlated with more urbanized municipalities but not with informal settlements. We highlight several factors that are counter-intuitively those most associated with high TB burdens and which should therefore play a large role in any effective targeting strategy. Targeting active case finding to key populations at higher risk of infection or poor clinical outcomes may prove more cost effective than broad efforts. However, these results should increase caution in current targeting of active case finding interventions.Item Do Incarcerated Populations Serve as a Reservoir for Tuberculosis in South Africa?(American Society of Tropical Medicine and Hygiene, 2018) Sharp, Alana; Donahoe, J. Travis; Milliken, Amanda; Barocio, Jacqueline; Charalambous, Salome; McLaren, ZoeTuberculosis (TB) prevalence among incarcerated populations is as much as 1,000 times higher than in the general population. This study evaluates whether correctional facilities serve as a reservoir through which TB is transmitted to surrounding communities. Tuberculosis test data were extracted from the South African National Health Laboratory Service database for patients tested for TB between 2005 and 2011. We conducted graphical analysis to assess the relationship of TB rates between incarcerated and non-incarcerated populations over time. We performed generalized linear modeling with a log link function to assess TB risk in communities surrounding correctional facilities, net of confounders. We assessed linkages between incarcerated and non-incarcerated populations over time using Granger causality analysis. Tuberculosis prevalence among incarcerated populations was four times higher than in the general population. Tuberculosis incidence rates in incarcerated and non-incarcerated populations followed similar trends over time. The presence of a correctional facility in a municipality was associated with 34.9% more detected TB cases (confidence interval: 11.6–63.2; P < 0.01), controlling for potential confounders. Detected TB in incarcerated populations did not have predictive power in explaining detected TB rates in the non-incarcerated population after controlling for serial correlation in the time series data. Despite high TB prevalence, trends in correctional facilities do not appear to be driving temporal trends in the general population. However, correctional facilities still act as a TB reservoir that raises the overall TB risk in the vicinity. Intensified TB control policies for correctional facilities, formerly incarcerated individuals, and surrounding communities will reduce TB prevalence overall.Item The Impact of Anti-Retroviral Therapy on Tuberculosis Detection at the National Level in South Africa(American Society of Tropical Medicine and Hygiene, 2018) McLaren, Zoe; Sharp, Alana; Brouwer, Elizabeth; Nanoo, AnantaHuman immunodeficiency virus/tuberculosis (HIV/TB) coinfection is particularly prevalent in South Africa, where TB has been the leading cause of death for more than a decade. The 2004–2008 national rollout of antiretroviral therapy (ART) provides a unique opportunity to examine the population-level impact of ART on the TB epidemic. We performed longitudinal regression analysis to follow the evolution of TB outcomes before and after the introduction of ART using a large data set from the National Health Laboratory Service. This is the first study to produce estimates of the impact of the ART rollout by exploiting staggered timing and geographic variation in the rollout. After ART became available in a health facility, 3.7% (P < 0.0001) more patients were tested for TB and 3.2% (P < 0.0001) more received repeat testing; however, there was a steep rise in testing before the introduction of ART. Although the number of TB-positive patients increased by 4.3% (P = 0.0002) in the first year post-ART, the TB rate among tested patients fell by 2 percentage points (8%, P = 0.001) after 2 years. Sputum smear testing declined relative to more technologically advanced diagnostics post-ART. Antiretroviral therapy availability increased the attention to TB screening and drew new patients into the health-care system. Small increases in the numbers of repeat patients are indicative of retention in care. The decline in TB rates post-ART suggests that the reduction in TB risk due to improved immune functioning and health-care contact likely outweighed the increased TB risk because of the longer lifespan of ART initiators.