Assessing the Value of Intensive Care.

Despite ongoing reform efforts, spending on hospital care in the United States remains an intractable problem.1 One strategy to lower hospital spending may be to reduce the number of intensive care unit (ICU) admissions, particularly for patientswith illnessof lowseverity who are admitted for observation rather than life-threateningorgan failure.2 Spending on hospital admissions involving intensive care accounts for nearlyhalf of all hospital costs,3making ICUadmissions an important focus for reducingoverall expenditures.At the same time, there is good evidence that intensive care is overused. Hospitals vary widely in their use of the ICU without apparent differences in mortality,4 and transient reductions in the availability of ICU beds leads to fewer ICU admissions without apparent harm topatients.5 These data imply that ICUadmissions fordiscretionarypatients, patients forwhomit is not clearwhether theywould benefitmore from ICU care or from care in thegeneralhospitalward, represent “low-value”health care—something to reduce if not eliminate all together. The usual prescriptions toward that end range fromexpanding the use of guidelines for ICU triage6 to forcingmore judicious use by reducing the availability of ICU beds.7 In this issueof JAMA, Valleyandcolleagues8 challenge this conventional wisdom by demonstrating a tangible benefit of ICU admission for a cohort of low-risk patients. The authors examined more than 1 million Medicare beneficiaries admittedto thehospitalwithpneumonia,andcompared30-daymortality between patients admitted to the ICU and patients admitted solely to thehospitalward.Toaccount for the selection bias inherent in this comparison they used an instrumental variable approach. Instrumental variables are an econometric technique for obtaining unbiased estimates of treatment effect in observational data.9 They exploit factors that are causally associatedwith treatment but not related to the outcome. Here the authors used an instrumental variable based on differential distance—the difference between (1) the patient’s home and the nearest hospital with high ICU admission rates and (2) the patient’s home and thenearest hospital. As shown in the Supplement to the article by Valley et al, this factor is strongly associatedwith ICU admission but is not associated without outcome except through ICU admission, meeting the criteria for a valid instrument. The study found that, in the instrumental variable analysis, admission to an ICU for patients with pneumonia whose need for ICU admission was borderline or discretionary was associated with a 5.7% absolute reduction in 30-day mortality, 14.8% for ICUadmissionvs 20.5% for generalward admission, comparedwith admission solely to a hospital ward. Additionally, therewereno statistically significant differences in total costs or total Medicare payments between groups, suggesting that ICU admission can save lives for lower-risk patients, and can do so at similar cost. If these results are valid, ICU admission for discretionary patients’ with pneumonia is the opposite of low-value care. It is high-value care,worth expanding rather than reducing. Before interpreting these results, it is important to consider to whom the analysis applies. Instrumental variable analyses only apply to the so-called “marginal” patient—in this study, patients for whom ICU admission is dependent upon their proximity to a hospital with a high rate of ICU utilization. This population is theoretical and cannot be explicitly defined. Intuitively, these patients should not have an obvious need for ICU admission (ie, shock or respiratory failure), but should be at sufficient risk for deterioration that they may benefit from careful monitoring and early intervention. However, the data in the report by Valley et al cannot reveal exactly who these patients are, or even how large the population may be. Using a standard approach, the authors estimated that this population may represent 13% of their cohort, or potentially 48 000Medicare beneficiaries per year. However, this estimate depends on the authors’ somewhat arbitrary definition of a hospital with high ICU admission rates, which they set at the top 40% of hospitals, corresponding to an ICU admission rate for patients with pneumonia of greater than 32%. The definition of a hospital with high ICU admission rates might plausibly vary based on any number of reasons, and thus the true marginal population could be either much bigger or much smaller. Thus it is not clear exactly how many lives might be saved by extending ICU admission to more discretionary patients. In addition to the caveats about generalizability, several other limitations areworthnoting. First, admission to the ICU may just be a proxy for individual or institutional commitment to full life support. Because this factor would be associated with both the instrument and with mortality, it would make ICUadmission appearmore beneficial than it really is.10 Second, because the analysis was limited to fee-for-service Medicare beneficiaries, it is uncertainwhether the results extend to other types of patients. Third, the finding that ICU admission was not associated with increased costs may understate truecost savings thatmightbeachieved throughavoiding ICUadmissions.Most ICUcosts are attributable toa fixedoverhead rather than individual patient care, andare thereforenot dependent on individual patient admissions.11 Thus, avoiding ICU admission might not be expected to reduce perpatient costs. Instead, cost savingswouldbeachievedover the long-term as ICUs decrease in size and the fixed costs deRelated article page 1272 Opinion