Estimating the effect of healthcare interventions on the distribution of health state severity for low back pain in the Global Burden of Disease study

Abstract

Background: Many causes of non-fatal health burden present with varying degrees of severity from asymptomatic to most severe. The severity distribution for diseases amenable to healthcare interventions is expected to vary as function of healthcare access and quality (HAQ). Current methods used in the Global Burden of Disease (GBD) study assume a constant severity distribution over space and time, ignoring any effect of healthcare interventions. This paper presents a method to incorporate information on the effect of healthcare interventions on health state severity and quantify the relationship between health state severity and HAQ in order to generate location-specific estimates of average condition severity. Using low back pain (LBP) as an example condition, estimates of intervention efficacy and utilization are generated and used to estimate averted and avoidable burden. Methods: Healthcare interventions for LBP were identified from the Cochrane Database of Systematic Reviews. Efficacy was assessed in terms of the standardized mean difference in disability relative to some usual care or placebo group. Interventions were grouped into five intervention classes: (1) surgical; (2) behavioral, cognitive, and physical therapies; and three classes of analgesics ((3) NSAID, (4) opioid, and (5) non-opioid non-NSAID analgesics). Effect sizes were pooled across all interventions in a class using a network meta-analysis framework. The overall treatment effect for LBP was calculated as the utilization-weighted sum of the intervention class effect sizes. The effect of treatment for LBP was also calculated assuming an aspirational 100% utilization of the optimal set of interventions among all individuals with LBP. The overall treatment effect was applied to the GBD LPB disability weight distribution generated from the United States based Medical Expenditure Panel Survey in order to estimate the relationship between intervention utilization and average disability. Using the Healthcare Access and Quality Index (HAQI) as a proxy for access to interventions for LBP, the relationship between HAQI and average LBP disability per case was linearly interpolated. For each country in the GBD, current YLDs, averted YLDs, avoidable YLDs, and YLDs for the optimal treatment scenario were calculated. Results: A total of 134 trials representing 160 unique intervention-comparison combinations were analyzed. Surgical interventions and NSAIDs were the most effective interventions (SMDs -0.44 (-0.70, -0.20) and -0.28 (-0.52, -0.04) respectively). The overall effect of healthcare interventions on LBP disability was estimated to be -0.17 (-0.35, 0.01) for LBP without leg involvement and -0.29 (-0.56, -0.01) for LBP with leg involvement. The maximum achievable proportion of LBP burden avoided through use of healthcare interventions under routine health care circumstances was 24.4% (1.4-41.3%) based on the relationship between HAQI and LBP disability. A hypothetical 100% utilization of the optimal treatment could avoid an additional 22.6% (4.1-31.2%) of LBP burden leaving 53.0% (28.0-95.4%) of LBP burden that cannot be addressed using existing healthcare interventions for LBP. Interpretation: Estimation of the relationship between intervention efficacy, utilization, and LBP severity indicates that health interventions impact LBP severity and imply that LBP severity should vary according to health system quality and intervention utilization. The methods presented in this study represent a generalizable approach to estimate location-specific severity distributions. Applied across the GBD, this method would allow for the estimation of averted and avoidable burden which serve as useful benchmarks for funders looking to expand coverage of and access to healthcare interventions. A reduction of the remaining burden which cannot be addressed using current healthcare technologies would require research and development to create novel approaches to treatment.