Our review of the empirical literature on the effects of P4P included all peer-reviewed published studies describing the impact of a hospital P4P program for either inpatient or outpatient hospital services. We defined outpatient hospital services as any medical or surgical services performed primarily in an outpatient/ambulatory care setting that are billed through a hospital. Examples of outpatient hospital services include chemotherapy, outpatient surgery, and diagnostic tests such as colonoscopy. The review included any randomized control studies, quasi-experimental trials, and pre-/post-intervention studies. We only retained articles that reported empirical findings related to the effect of paying for quality, patient experience, and safety or resource use, specifically excluding articles focused only on the impact of changes in hospital payment, such as the shift to the Prospective Payment System (PPS) and P4P as applied to physicians in the ambulatory setting. Only studies that were in English and published in the last 10.5 years were included.
We searched for articles published between January 1996 and June 2007 using five bibliographic databases (PubMed, EconLit, CINAHL, Psycinfo, and ABInform) that could include articles related to P4P and financial incentives specific to the hospital environment. Table 2 displays the search strategy and terms used to identify relevant articles for hospital inpatient and hospital outpatient settings separately.
|pay for performance OR p4p OR “pay for quality” OR “pay for value” OR “value based purchasing” OR “financial incentives” OR “monetary incentives”||“pay for performance” OR p4p OR “pay for quality” OR “pay for value” OR “value based purchasing” OR “financial incentives” OR “monetary incentives”|
|(bonus* OR reward* OR (incentive reimbursement)) AND quality||This resulted in a database of 1,575 articles. Within this database, we retained any article that included the following keywords:
|hospital OR hospitals|
|(Results from search #1 or #2) AND (Results from Search #3)|
|NOT (organ donation)|
We combined the results of this search strategy for each setting (conducted initially in November 2006 and update with articles published through June 2007) from the five different databases and then eliminated duplicate articles. Titles and abstracts for these articles were reviewed, and potentially eligible articles were identified. The full text of the set of potentially eligible articles was then read to determine whether the article was appropriate for inclusion. Reference lists of the included articles were checked to identify additional relevant studies. To ensure our scan was comprehensive, we also consulted experts in the field of P4P and retrieved references from recent reports on P4P and payment reform from the IOM, the Joint Commission, MedPAC, and the Agency for Healthcare Research and Quality (AHRQ).
From the initial search strategy, we identified 902 non-duplicated articles for the hospital inpatient setting and 162 non-duplicated articles for the hospital outpatient setting. After the abstracts were reviewed, eleven articles were targeted for further review for the inpatient setting and zero for the hospital outpatient setting. Of the eleven articles, eight met our criteria for inclusion. After consultation with P4P experts and a review of relevant reports, one more paper was thought to be sufficiently important to include. It is a white paper, not published in the peer-reviewed literature, describing the early results of the CMS–Premier Hospital Quality Incentive Demonstration (PHQID). Our summary therefore focuses on the findings from nine articles that describe P4P intervention in the inpatient setting.
The methodological quality of the articles was assessed by evaluating the overall study design in terms of its strength in determining a causal relationship or an association between the intervention and the outcome. For example, we determined whether the study design was a pre-post measurement without a control group, a pre-post study with a control group (a quasi-experimental study design), or a randomized control trial. If there was a control group, we also assessed its adequacy, such as whether hospitals in the control group were reasonably similar to hospitals exposed to the P4P intervention. If there was no control group, we assessed whether the study controlled for pre-intervention trends in performance. Lastly, we assessed the studies’ use of appropriate statistical methods for estimating an intervention effect. These characteristics were used to determine the quality of the studies being reviewed, with randomized control trials providing the strongest evidence of a causal relationship between the implemented program and changes in performance measures, and uncontrolled studies providing weaker evidence.