James Lomas’s journal round-up for 21st May 2018

Every Monday our authors provide a round-up of some of the most recently published peer reviewed articles from the field. We don’t cover everything, or even what’s most important – just a few papers that have interested the author. Visit our Resources page for links to more journals or follow the HealthEconBot. If you’d like to write one of our weekly journal round-ups, get in touch.

Decision making for healthcare resource allocation: joint v. separate decisions on interacting interventions. Medical Decision Making [PubMed] Published 23rd April 2018

While it may be uncontroversial that including all of the relevant comparators in an economic evaluation is crucial, a careful examination of this statement raises some interesting questions. Which comparators are relevant? For those that are relevant, how crucial is it that they are not excluded? The answer to the first of these questions may seem obvious, that all feasible mutually exclusive interventions should be compared, but this is in fact deceptive. Dakin and Gray highlight inconsistency between guidelines as to what constitutes interventions that are ‘mutually exclusive’ and so try to re-frame the distinction according to whether interventions are ‘incompatible’ – when it is physically impossible to implement both interventions simultaneously – and, if not, whether interventions are ‘interacting’ – where the costs and effects of the simultaneous implementation of A and B do not equal the sum of these parts. What I really like about this paper is that it has a very pragmatic focus. Inspired by policy arrangements, for example single technology appraisals, and the difficulty in capturing all interactions, Dakin and Gray provide a reader-friendly flow diagram to illustrate cases where excluding interacting interventions from a joint evaluation is likely to have a big impact, and furthermore propose a sequencing approach that avoids the major problems in evaluating separately what should be considered jointly. Essentially when we have interacting interventions at different points of the disease pathway, evaluating separately may not be problematic if we start at the end of the pathway and move backwards, similar to the method of backward induction used in sequence problems in game theory. There are additional related questions that I’d like to see these authors turn to next, such as how to include interaction effects between interventions and, in particular, how to evaluate system-wide policies that may interact with a very large number of interventions. This paper makes a great contribution to answering all of these questions by establishing a framework that clearly distinguishes concepts that had previously been subject to muddied thinking.

When cost-effective interventions are unaffordable: integrating cost-effectiveness and budget impact in priority setting for global health programs. PLoS Medicine [PubMed] Published 2nd October 2017

In my opinion, there are many things that health economists shouldn’t try to include when they conduct cost-effectiveness analysis. Affordability is not one of these. This paper is great, because Bilinski et al shine a light on the worldwide phenomenon of interventions being found to be ‘cost-effective’ but not affordable. A particular quote – that it would be financially impossible to implement all interventions that are found to be ‘very cost-effective’ in many low- and middle-income countries – is quite shocking. Bilinski et al compare and contrast cost-effectiveness analysis and budget impact analysis, and argue that there are four key reasons why something could be ‘cost-effective’ but not affordable: 1) judging cost-effectiveness with reference to an inappropriate cost-effectiveness ‘threshold’, 2) adoption of a societal perspective that includes costs not falling upon the payer’s budget, 3) failing to make explicit consideration of the distribution of costs over time and 4) the use of an inappropriate discount rate that may not accurately reflect the borrowing and investment opportunities facing the payer. They then argue that, because of this, cost-effectiveness analysis should be presented along with budget impact analysis so that the decision-maker can base a decision on both analyses. I don’t disagree with this as a pragmatic interim solution, but – by highlighting these four reasons for divergence of results with such important economic consequences – I think that there will be further reaching implications of this paper. To my mind, Bilinski et al essentially serves as a call to arms for researchers to try to come up with frameworks and estimates so that the conduct of cost-effectiveness analysis can be improved in order that paradoxical results are no longer produced, decisions are more usefully informed by cost-effectiveness analysis, and the opportunity costs of large budget impacts are properly evaluated – especially in the context of low- and middle-income countries where the foregone health from poor decisions can be so significant.

Patient cost-sharing, socioeconomic status, and children’s health care utilization. Journal of Health Economics [PubMed] Published 16th April 2018

This paper evaluates a policy using a combination of regression discontinuity design and difference-in-difference methods. Not only does it do that, but it tackles an important policy question using a detailed population-wide dataset (a set of linked datasets, more accurately). As if that weren’t enough, one of the policy reforms was actually implemented as a result of a vote where two politicians ‘accidentally pressed the wrong button’, reducing concerns that the policy may have in some way not been exogenous. Needless to say I found the method employed in this paper to be a pretty convincing identification strategy. The policy question at hand is about whether demand for GP visits for children in the Swedish county of Scania (Skåne) is affected by cost-sharing. Cost-sharing for GP visits has occurred for different age groups over different periods of time, providing the basis for regression discontinuities around the age threshold and treated and control groups over time. Nilsson and Paul find results suggesting that when health care is free of charge doctor visits by children increase by 5-10%. In this context, doctor visits happened subject to telephone triage by a nurse and so in this sense it can be argued that all of these visits would be ‘needed’. Further, Nilsson and Paul find that the sensitivity to price is concentrated in low-income households, and is greater among sickly children. The authors contextualise their results very well and, in addition to that context, I can’t deny that it also particularly resonated with me to read this approaching the 70th birthday of the NHS – a system where cost-sharing has never been implemented for GP visits by children. This paper is clearly also highly relevant to that debate that has surfaced again and again in the UK.



Review: Health Econometrics Using Stata (Partha Deb et al)

Health Econometrics Using Stata

Partha Deb, Edward C. Norton, Willard G. Manning

Paperback, 264 pages, ISBN: 978-1-59718-228-7, published 31 August 2017

Amazon / Google Books / Stata Press

This book is the perfect guide to understanding the various econometric methods available for modelling of costs and counts data for the individual who understands econometrics best after applying it to a dataset (like myself). Pre-requisites include a decent knowledge of Stata and a desire to apply econometric methods to a cost or count outcome variable

It’s important to say that this book does not cover all aspects of econometrics within health economics, but instead focuses on ‘modelling health care costs and counts’ (the title of the short course from which the book evolved). As expected from this range of texts, the vast majority of the book comes with detailed example Stata code for all of the methods described, with illustrations either using a publicly available sample of MEPS data or simulated data.

Like many papers in this field, the focus of the book revolves around the non-normal characteristics of health care resource use distributions. These are the mass point at zero, right-hand skew and inherent heteroskedasticity. As such the book covers the broad suite of models that have been developed in order to account for these features, ranging from two-part models, transformation of the data (and the problematic re-transformation of estimated effects) to non-linear modelling methods such as generalised linear models (GLMs). Unlike many papers in this field, the authors emphasise the need – and provide guidance on how – to delve deep into the underlying data in order to appreciate the most appropriate methods (there is even a chapter on design effects) and encourage rigorous testing of model specification. In addition, Health Econometrics Using Stata considers the important issue of endogeneity and is not solely fixated on distributional issues, providing important insight and code for estimation of non-linear models that control for potential endogeneity (interested readers may wish to heed the published cautionary notes for some of these methods, e.g. Chapman and Brooks). Finally, the book describes more advanced methods for estimating heterogeneous effects, although code is not provided for all of these methods, which is a bit of a shame (but perhaps understandable given the complexity).

This could be a very dry text, but it is not – emphatically! The personality of the authors comes through very strongly from the writing. Reading it brought back many pleasant memories from the course ‘modelling health care costs and counts’ that I sat in 2012. The book also features a dedication to Willard Manning, which is a fitting tribute to a man who was both a great academic and an outstanding mentor. One particular highlight, with which past course attendants will be familiar, is the section ‘top 10 myths in health econometrics’. This straightforward and punchy presentation, backed up by rigorous methodological research, is a great way to get these key messages across in an accessible format. Other great features of this book include the use of simulations to illustrate important features of the econometric models (with code provided to recreate) and a personal highlight (granted, a niche interest…) was the code to generate appropriate standard errors when using the poisson family within GLMs for costs.

Of course, Health Econometrics Using Stata cannot be comprehensive and there are developments in this field that are not covered. Most notably, there is no discussion of how to model these data in a panel/longitudinal setting, which is crucially important for estimating parameters for decision models, for example. Potential issues around missing data and censoring are also not discussed. Also, this text does not cover advances in flexible parametric modelling, which enable modelling of data that are both highly skewed and leptokurtic (see Jones 2017 for an excellent summary of this literature along with a primer on data visualisation using Stata).

I heartily recommend Health Econometrics Using Stata to interested colleagues who want practical advice – on model selection and specification testing with cost and count outcome data – from some of the top specialists in our field, in their own words.