Tabiri, S., Jalali, A., Nelson, R.E. et al. ``Barriers to Timely Presentation of Patients with Surgical Conditions at Tamale Teaching Hospital in Northern Ghana.’’ World Journal of Surgery (2019) 43: 346 - 352

Tabiri, S., Yenli, M., Jalali, A., et al. ``The use of mesh for inguinal hernia repair in northern Ghana.’’ J Surgical Research (2018) 230: 137-142

Tabiri S, Russell KW, Gyamfi FE, Jalali A, Price RR, Katz MG. ``Local anesthesia underutilized for inguinal hernia repair in northern Ghana.’’ PLoS ONE (2018): 13(11): e0206465.

Goz, V., Lakomkin, N., Jalali, A., Brodke, D. S., & Spiker, W. R. (2018). Coagulation Laboratory Testing Is Predictive of Wound Complications Following Microdiscectomy. Global Spine Journal (2018).

Papers Under Review

Minimum Wage and Infant Mortality: Estimates Using Contiguous County-pairs

Journal: Journal of Human Resources

Interest in the non-economic impact of minimum wage laws have led to a growing literature examining how population health measures respond to state minimum wage increases in the US. These studies rely on the canonical two-way fixed effect estimator, which is an unreliable method to infer causal effects with spatially heterogeneous populations. In this paper, I study the impact of minimum wage differences across states and within-state ordinances on infant mortality rates. I isolate the causal effect of the minimum wage by employing a spatial regression discontinuity design using contiguous counties in different states that share a common state border as local treatment and control populations. I find that a 10 percent increase in local cost-of-living adjusted minimum wage reduces infant mortality rates by 3.2 percent among lower-educated mothers--a group more likely affected by minimum wage changes. I find that reductions in infant mortality is concentrated in the post-neonatal period. I also demonstrate that the traditional empirical approach employed in this literature will produce lower estimates of the health impact of the minimum wage. My findings provide robust evidence that minimum wage increases are causally linked with improved infant health.

Provider Practice Competition and Adoption of Medicare's Oncology Care Model

Journal: Medical Care (Revise and Resubmit)


Background: There is concern that the Oncology Care Model (OCM), a voluntary bundled payment program, may incentivize mergers and acquisitions among physician practices leading to reduced competition and price increases. These concerns are heightened if OCM is preferentially adopted in competitive healthcare markets, but little is known about the characteristics of markets where OCM is adopted. 

Objective: We test the hypothesis that adoption of OCM was greater in more competitive medical oncologist markets.

Research Design: The Herfindahl-Hirschman Index (HHI), a measure of competition, was calculated for Hospital Referral Regions (HRRs) using secondary data from the Centers for Medicare and Medicaid Services. The relationship between HHI and OCM adoption was assessed using a two-part regression model adjusting for market-level number of practices, physician density, average practice size, sociodemographic characteristics, and medical resources. 

Subjects: 10,788 providers who billed Medicare for oncology services in 2015. 

Results: OCM was adopted in 114 (37%) of the 306 HRRs. Practices in competitive healthcare markets were more likely to adopt OCM than in non-competitive markets with a 15.7 percent difference in the predicted probability of adoption comparing the interquartile range of HHI. Average size and number of practices in an HRR were positively associated with adoption, while rate of full-time equivalent hospital employees to 1,000 residents was negatively associated with adoption.

Working Papers

Subjective Life Expectancy as a Source of Health Disparities?

A large volume of literature links social and economic factors with mortality and life expectancy. This essay examines to what extent these socio-economic factors, specifically income, impact subjective life expectancy (SLE) or an individual’s belief in surviving to a certain age. I first develop a model to describe how SLE may play an important role in linking wage increases to favorable health behavior by making future time costs of adverse health events binding. I then estimate a heterogeneous choice proportional odds model using previously unexplored data from the Federal Reserve's 2013 Survey of Household Economics and Decision-making (SHED) to study this relationship. I find that Income and higher education is strongly associated with improved confidence in survival to age 75. I also find that periods of unemployment, disability, divorce, negative life event associated with the great recession were negatively associated with SLE. My study contributes to the health disparities literature by providing evidence for a new channel connecting socio-economic factors and health outcomes. 

Cost of Primary Single Level Lumbar Discectomy

Objective: Improving value in surgical care requires a detailed understanding of the true costs of surgical and operating room resources. In this study, we sought to identify predictors of healthcare costs and operating room resource use for patients undergoing initial single-level discectomies using a unique institutional cost dataset from the Value Driven Outcomes (VDO) program developed by the University of Utah.

Subjects: 622 patients undergoing initial single-level lumbar discectomy between January 2014 to April 2016 at the University of Utah Orthopaedic Center.

Methods: Univariate and multivariate Generalized Linear Models (GLM) performed to identify predictors of healthcare costs, clinical length of stay (LOS, days) and operating room time (OR, minutes) using a unique costing tool. Modified park test procedure was implemented to determine GLM error distribution specifications and standard errors were clustered by provider. Cost outcomes were normalized using mean costs for a patient with normal Body Mass Index (BMI) and a healthy American Society of Anesthesiologists (ASA) classification system. Average marginal effects in multivariate analysis were reported as percentage of normalized costs.

Results: Advanced age, male gender, Hispanic, Black, unemployment, and being retired were significant positive predictors of costs in univariate analysis. Asian, Native American, outpatient procedures, and being a student were significant negative predictors of costs. Univariate analysis also showed that obesity, higher ASA class and insurance status were also positive and significant predictors of costs. In multivariate analysis, we found that obesity led to higher average marginal total direct (9%), total facility (15%), and facility OR costs (22%), as well as an average marginal effect of 24 more OR minutes per surgery. Conversely, being underweight was associated with lower average marginal total direct (-23%), total non-facility (-54%), total facility (-8%), facility OR costs (-15%), as well as lower clinical LOS (-.42 days), and 18 less OR minutes. While being overweight was not significantly associated with greater total direct costs, it was associated with higher total facility (8%), and facility OR costs (12%), with an average marginal effect of 11 more OR minutes per surgery. Age was associated with a longer LOS but not with OR costs in multivariate analysis. As expected, outpatient surgical costs, LOS and OR time were significantly lower than inpatient procedures. [w1] Patients with Incapacitating disease ASA Class had the highest predicted OR time in GLM estimates with an average marginal effect of 28 minutes, while Severe systematic disease was associated with greater total and non-facility costs. In addition, Medicare patients had higher facility costs (14%) compared to privately insured patients.

Conclusions: Although many of our observed variables were significant predictors of costs in univariate analysis, multivariate GLM estimates showed that the main variables determining cost and operating room time and resource use were Obesity (BMI), General Health (ASA class), Medicare status and advanced age, and whether the surgery was an outpatient or inpatient procedure.

Cost-effectiveness Analysis of Drug Therapy for Infantile-onset Spinal Muscular Atrophy: The Role of Newborn Screening.

Background:Spinal muscular atrophy (SMA), an autosomal neuromuscular disorder, is one of the leading genetic contributors to infant mortality. Infantile-onset SMA is the most severe type of SMA and the median survival time for children with this condition is typically less than 2 years of age. Currently, only a handful of states in the US screen for SMA as part of their universal newborn screening program. However, with the introduction of new treatment options, SMA has been added to the federal Recommended Uniform Screening Panel (RUSP). Despite efficacy, the high price of drug therapy (nusinersen) has led health authorities in Canada and the UK to doubt its cost-effectiveness given the costs of treatment. This study estimates the cost-effectiveness of nusinersen drug therapy of patients with infantile-onset SMA and examines whether expanded newborn screening can improve the economic value of nusinersen.

Methods:We developed a decision analytic Markov model to estimate the expected costs and health benefits of infantile-onset SMA with an initial time horizon of 2.5 years and projected lifetime costs and health outcomes until death for a hypothetical cohort of 100,000 live births. Model inputs were derived from the literature with the main treatment-related parameters derived from the ENDEAR trial results and preliminary results of the NURTURE trial. Primary outcomes were cost per event-free (without permanent ventilator assistance) life-years (LY) and quality adjusted life-years (QALY) saved with newborn screening and drug therapy compared to drug therapy without screening or neither treatment nor screening. 

Results:The estimated incremental cost-effectiveness ratio (ICER) for nusinersen drug therapy without screening was $508,481 per event-free LY saved and $522,118 per event-free QALY saved relative to no treatment. The ICERs for screening newborns along with treatment as compared to treatment without screening were $193,867 per event-free LY saved and $199,510 per event-free QALY saved using base-case ENDEAR results. Compared to a common baseline of no treatment or screening, the ICER for nusinersen with screening was $339,793 per event-free LYs saved, which is $169,000 less than treatment alone. The mixed strategy of no treatment without screening and treatment with screening eliminated from consideration the strategy of treatment without screening in our base case model. All our estimates are greater than standard willingness-to-pay (WTP) thresholds. However, we find that at a per-dose price of $32,250, screening and treatment is a cost-effective strategy given a WTP threshold of $50,000 per event-free LY saved. Using preliminary data from the NURTURE trial indicated an 85.7% improvement in expected LY saved compared to our base results.

Conclusion:This study provides the first estimates of the cost-effectiveness of SMA drug therapy combined with newborn screening.  We find that the per-dose price of drug therapy is too high for treatment to be considered cost-effective by standard WTP thresholds. However, our results suggest that newborn screening along with drug therapy reduces the estimated ICER for treating a patient with SMA compared to treatment alone.  We conclude that expanding newborn screening to include SMA provides improved economic value for payers and patients if nusinersen is made available to patients.

Cost effectiveness of current and potential serum based colorectal screening strategies: can a serum based test do better?

Background: Despite efficacy of colorectal cancer (CRC) screening, recent trends in screening rates have not improved. Furthermore, national society recommendations have not prioritized a single screening modality. Both flexible sigmoidoscopy (Flex-Sig) and guaiac fecal occult blood test (gFOBT)) have been recommended. Studies suggest that noninvasive tests may improve screening rates, however, compliance remains modest for such tests. A recent study found that health system transition from gFOBT to a fecal immunochemical test (FIT) moderately improved test compliance rates. However, FIT is an expensive substitute for gFOBT and sensitivity of fecal based tests for precursor lesions in the colon remain inferior to structural examinations. Serum-based blood tests (SBT) may provide higher compliance rates, but necessary accuracy for such a test to be a dominant or cost-effective screening strategy over current recommendations have not been determined. This study analyzed the cost-effectiveness of multiple CRC screening strategies and estimated minimum test characteristics of a hypothetical SBT to be a preferred screening strategy over current modalities.

Methods: A Markov microsimulation model was developed to analyze the costs and effects, (quality-adjusted life-years, QALYs) of CRC screening following a hypothetical cohort of 10,000 individuals at age 50 until death. Our model considered three strategies: 1) initial colonoscopy followed by Flex-Sig every 5 years, 2) initial colonoscopy with yearly gFOBT, and 3) initial colonoscopy with yearly FIT. An initial colonoscopy with a hypothetical yearly SBT was also examined at a range of test sensitivities. A long-term payer perspective was assumed for professional and facility costs and lifetime costs of cancer treatment. Model probabilities and utility values were obtained from the literature or calculated from National Vital Statistics Reports. 

Results: Annual gFOBT was the least costly strategy ($3,242) while annual FIT was eliminated through extended dominance. Flex-Sig was the costliest strategy at $4,667 but had the highest expected QALYs at 19.68. The incremental cost-effectiveness ratio (ICER) of Flex-Sig relative to gFOBT was $35,615. Our secondary analysis demonstrated that a minimum joint sensitivity of 70% and 60% is required for an SBT at 80% and 100% compliance rates, respectively, to achieve extended dominance of both Flex-Sig and FIT by SBT and gFOBT. ICER’s of SBT ranged from $12,984 to $4,779 in these sensitivity ranges compared to gFOBT with expected QALYs as high as 19.96. Total individual costs in the model varied from $365 to $111,535.

Conclusion: With improved sensitivity and high compliance rates, annual screening for CRC via a non-invasive SBT is a cost-effective approach compared to structural examinations and currently recommended gFOBT and FIT.