Exploration of this quality-quantity relationship adds to such findings by evaluating whether under- or over-provision is likely to be of greater concern to policymakers. By distinguishing between when more healthcare is desirable as compared with more care being unnecessary, it also contributes to the efficiency literature.

To evaluate the extent to which doctors provide too little or too much care, we used clinical performance vignettes (CPVs), whereby physicians were asked how they would care for a range of paediatric cases [3]. These CPV responses were disaggregated into components that distinguish insufficient and unnecessary care. Accordingly, the objective of this research is to provide insights into the different components of sub-optimal quality of care.

Results also showed that moving from insufficient to sufficient care can bring large health gains for the patient without much additional expense to the patient. However, as discussed earlier, the total cost of this move to sufficient care will depend on how costly it proves to change provider behaviour. This includes the costs of training and other quality improving strategies which have been shown to be effective. For example, a recent review of studies found that supervision and audit with feedback were two of the more effective ways to improve health worker performance, and that dissemination of treatment guidelines, self-assessment, and training were much more effective when combined with appropriate supervision [11]. However, supervision costs have been considered expensive from studies on supervision that have reported its costs [12].

In contrast, reducing unnecessary care can lead to important cost savings, but it does not always offer substantial health gains. That is, unnecessary care often reflected ‘flat-of-the-curve’ medicine and healthcare that are not harmful but equally provide no incremental benefit to the patient [13]. The cost of such unnecessary care can be substantial: for instance, the World Health Report 2010 estimated that at least 20–40% of total health spending is ineffectively spent. Moreover, it identified overuse of medicines, healthcare products and services, and medical errors as some of the leading sources of inefficiency [14].

Thus insufficient care is more likely to have worse health consequences for the patient than unnecessary care. An important caveat is that unnecessary care often took the form of doctors recommending antibiotics (i.e. 47% of the time). Although judged by physicians to be mostly health neutral on a case-by-case basis, overuse of antibiotics is a public health concern because it can expose the population as a whole to higher antibiotic resistance, and can be costly [15, 16]. Further, patients were unnecessarily hospitalized 34% of the time. This was also judged to be health neutral, but unnecessary hospitalization increases the risk of individuals acquiring nosocomial infections or having further unnecessary tests and procedures. Finally, we did not find substantive differences in practices between public vs. private practitioners.

The study has some potential limitations. First, CPVs are based on hypothetical behaviour, with some authors arguing that they only measure a doctor's health knowledge [17]. However, previous research has shown CPVs to be a valid measure of process quality in healthcare, outperforming chart abstraction when compared with the gold standard of the ‘standardized patient’ [3]. This study was repeated in a larger number of settings with a broader range of conditions in a second validation study [18]. The results of the second trial confirmed that performance measured by CPVs came close to (and did not exceed) actual practice. This validation work involved over 200 doctors and 16 different conditions and over 1500 patients. Still, it is recognized that no studies have to date validated CPVs against standardized patients in lower income country settings. Second, CPVs are limited to evaluating the technical quality of healthcare, with no analysis of interpersonal quality. Vignettes also analyse only a selection of conditions. Still, paediatric pneumonia and diarrhoea, analysed here, are common conditions in low- and middle-income countries, the leading causes of death in this population and thus represent a high burden of disease where appropriate clinical care improves a patient's health outcome. These clinical conditions are thus likely to be good ‘tracer’ conditions in evaluating the broader health system [19, 20], although they are less representative of adult care, particularly chronic conditions.

The design of this analysis also had its own specific limitations. First, only one dimension of care—a doctor's recommended treatment plan—was analysed. Even though inclusion of diagnostic testing would look at additional costs, a doctor's treatment plan is the most relevant dimension for analysing costly and potentially harmful consequences of overprovision, and consequently the relationship between quality and quantity of care. Second, measures of the overall extent of both insufficient and unnecessary care were simple aggregates. Other CPV studies, addressing different issues, have used expert panels [3] or item response theory [21] to weight doctor's responses. Although in this research there was no weighting of individual items as contributors to a single CPV score, the expected health and cost consequences of these individual items were evaluated. More generally, the study was set in the Philippines. Whilst we believe our general findings about the nature of the quality–quantity relationship are likely to be applicable to other country contexts, we realize that this merits further attention. For instance, studies have consistently shown that provider payment mechanisms influence the quantity of care a doctor provides [22]. Consequently, variation in the exact mix of insufficient and unnecessary care may vary across countries because of different mixes in provider payments.

Notwithstanding these limitations, this research adds to the literature by simultaneously investigating insufficient care and unnecessary care. Existing research has typically evaluated the extent of insufficient care or unnecessary care, but not both at the same time. For instance, in other studies that have used CPVs, a doctor's technical quality of care is assessed by analysing whether s/he has provided a comprehensive set of actions needed to improve a patient's health (e.g. [15, 23]), and if not, which actions they did not provide. But no distinction is made in these studies between a doctor failing to recommend a needed treatment (or other action), and a doctor recommending an unnecessary treatment.

Indeed, most studies measuring the technical quality of healthcare can be understood as focusing on the extent of insufficient care, with no direct analysis of unnecessary care. Structural quality measures can (at best) assess whether doctors are likely to be constrained in their attempts to provide comprehensive care (e.g. [24]). Related QIDS research analysed the impact of structural factors on quality of care in the same study area as our paper. They found that staffing levels, medical supplies and other structural factors had little impact on quality of care [25]. However, structural quality measures provide no information on the potential for over-provision. Studies using other process quality measures—such as chart abstraction [26], direct observation [17] and standardized patient approaches [27]—can also be interpreted in the same way. That is, they compare a doctor's healthcare provision against a checklist of required actions, with the focus being on which aspects of this checklist the doctor failed to complete. Outcome measures could ultimately provide the most accurate measure of healthcare quality. However, they cannot easily separate out the impact (positive or negative) of individual aspects of a doctor's treatment plan on a patient's health.

In contrast, the literatures on health provider efficiency and supplier-induced demand assess unnecessary care but not insufficient care. The sole focus of the supplier-induced demand literature is on whether, and if so how, doctors can influence patients to utilize more healthcare than is clinically necessary [28]. The efficiency literature has shown that hospitals (as a whole) have some costs that are due to waste or poor decision-making. But most of these efficiency studies implicitly assume adequate quality [29]. Some efficiency studies do account for quality, and consequently the possibility of insufficient care [30–32]. Nevertheless, these studies concentrate on identifying when quantity of care can be reduced without negatively impacting upon healthcare quality, rather than on quality directly.