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Postoperative VTE rate may not be accurate hospital quality measure
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Increased adherence to postoperative venous thromboembolism prophylaxis positively correlated with event rates, prompting researchers to question whether the rate of postoperative blood clots should be used as a hospital quality measure.
The Agency for Healthcare Research and Quality developed a risk-adjusted measure of postoperative venous thromboembolism (VTE), and the measure has been incorporated into many public reporting initiatives and quality improvement efforts, according to background information provided by researchers.
“However, measuring VTE rates may be flawed because of surveillance bias, in which variation in outcomes reflects variation in screening and detection — or ‘the more you look, the more you find’ phenomenon,” the researchers wrote.
Karl Y. Bilimoria
Karl Y. Bilimoria, MD, MS, assistant professor of surgical oncology and director of the Surgical Outcomes and Quality Improvement Center at Northwestern University Feinberg School of Medicine, and colleagues conducted the investigation to examine whether surveillance bias influences the authenticity of reported VTE rates.
The researchers used 2010 Hospital Compare and American Hospital Association data on 2,838 hospitals. They used 2009-2010 Medicare claims data on 954,926 surgical patient discharges to calculate VTE imaging and event rates.
Hospitals in the highest imaging rate quartile diagnosed 13.5 VTEs per 1,000 discharges, whereas hospitals in the lowest imaging rate quartile diagnosed 5 VTEs per 1,000 discharges (P<.001).
Researchers observed a weak association between greater hospital VTE prophylaxis adherence rates and worse risk-adjusted VTE event rates (P=.03).
Hospitals with higher structural quality scores demonstrated better VTE prophylaxis adherence rates (95.5% for the highest quartile vs. 93.3% for the lowest quartile; P<.001), but those hospitals also had higher risk-adjusted VTE rates (6.4 per 1,000 for the highest quartile vs. 4.8 per 1,000 for the lowest quartile; P<.001).
Researchers also observed considerable variation in mean VTE diagnostic imaging rates (167 studies per 1,000 in the highest quartile vs. 32 per 1,000 in the lowest quartile; P<.001).
“Hospitals reported to have the highest risk-adjusted VTE rates may in fact be providing vigilant care by ordering imaging studies to ensure that VTE events are not missed,” Bilimoria and colleagues wrote. “Patients selecting hospitals according to publicly available metrics may be misled by currently reported VTE performance. The measure could be counterproductive if a hospital performs poorly on the VTE outcome metric, expends efforts to improve VTE prophylaxis — resulting in increased awareness and vigilance in looking for VTE — and then finds more VTEs and becomes an even worse performer on the VTE measure.”
In an accompanying editorial, Edward H. Livingston, MD, FACS, professor of surgery and biomedical engineering at the University of Texas Southwestern School Of Medicine and deputy editor of JAMA, agreed physicians who more aggressively look for complications frequently find more and appear to have worse outcomes.
“Less obvious in the data from Bilimoria et al is that the very high compliance rate with VTE prophylaxis might result from many patients receiving treatments from which they are not likely to benefit,” Livingston wrote. “This is because current process measures were based on older guidelines that overestimated the benefits of VTE prophylaxis. Public reporting of VTE rates should be reconsidered or curtailed because few hospitals have sufficient numbers of patients to show statistically significant effects of prophylactic measures on VTE rates.”
For more information:
- Bilimoria KY. JAMA. 2013;doi:10.1001/jama.2013.280048.
- Livingston EH. JAMA. 2013;doi:10.1001/jama.2013.280049.
Disclosure: See the full study for a list of the researchers’ relevant financial disclosures.