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Research Briefs

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Bryce, C.L., Engberg, J.B., and Wholey, D.R. (2000, June). "Comparing the agreement among alternative models in evaluating HMO efficiency." (AHRQ grant HS09200). Health Services Research 35(2), pp. 509-528.

These authors use alternative models—data envelopment analysis (DEA), stochastic production frontiers (SPF), and fixed-effects regression (FER)—for evaluating the efficiency of health maintenance organizations (HMOs) using a nationwide sample of HMOs. These approaches all assume that output is homogeneous. Researchers therefore must choose a way to model efficiency as well as a method to adjust for differences in output quality and case mix. These researchers compared the results of these alternative models in terms of individual performance and industry-wide trends. All three models identified similar trends for the HMO industry as a whole. However, they assessed the relative technical efficiency of individual firms differently. Thus, these techniques are limited for either benchmarking or setting rates. While concurrence among techniques is no guarantee of accuracy, it can be reassuring. Conversely, radically distinct inferences across models can be a warning to temper research conclusions.

Fiser, D.H., Tilford, J.M., and Roberson, P.K. (2000). "Relationship of illness severity and length of stay to functional outcomes in the pediatric intensive care unit: A multi-institutional study." (AHRQ grant HS09055). Critical Care Medicine 28(4), pp. 1173-1179.

Mortality by itself is probably not a sufficient indicator of outcomes for pediatric intensive care units (PICUs) because it is a relatively rare event. Supplementing mortality data with functional outcomes data can provide a broader view of unit performance, according to these researchers. They used multi-institutional data to study the relationships between illness severity, length of stay, and functional outcomes among 11,106 patients at 16 PICUs across the United States. They measured functional outcomes by the Pediatric Overall Performance Category (POPC) and Pediatric Cerebral Performance Category (PCPC) scales at baseline and discharge from the PICU. Baseline, discharge, and delta POPC and PCPC outcome scores were associated with length of stay in the PICU and with predicted risk of mortality. Moderate and severe baseline deficits for both the POPC and PCPC score predicted increased length of stay between 30 and 40 percent. The authors conclude that the POPC and PCPC outcome scales can be used as reference values for evaluating clinical programs or for clinical outcomes research.

Hoffman, J.R., Mower, W.R., Wolfson, A.B., and others. (2000, July). "Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. National Emergency X-Radiography Utilization Study Group." (AHRQ grant HS08239). New England Journal of Medicine 13, pp. 94-99.

Because of their fear of missing a diagnosis of cervical spine injury (which can produce catastrophic neurologic disability) in blunt trauma victims, doctors obtain cervical spine x-rays on virtually all such patients. However, this study shows that a decision instrument that uses a small set of clinical criteria can identify most cervical spine injury victims without x-rays. The researchers examined the ability of a decision instrument to detect cervical spine injury among 34,069 blunt trauma victims undergoing cervical spine x-rays (including 818 with cervical spine injury) at 21 medical centers across the United States. The decision instrument identified all but 8 of the cervical spine injury victims, for a near 100 percent sensitivity for detecting clinically important injuries. Based on classification by the decision instrument, 13 percent of blunt trauma victims could have been spared x-ray imaging.

Kovner, C., Mezey, M., and Harrington, C. (2000, first quarter). "Research priorities for staffing, case mix, and quality of care in U.S. nursing homes." (AHRQ grant HS09814). Journal of Nursing Scholarship, pp. 77-80.

Nursing homes are being called on to care for a more acute and diverse mix of patients, who by nature of their health conditions use more resources than nursing home residents of 10 years ago. These authors describe research priorities for studies on staffing, case mix, and quality of care in U.S. nursing homes. They point out that variations in health problems of people in nursing homes require any analysis of staffing and quality to include an adjustment for case mix. Research on staff should include a mix of RNs, LPNs, nursing assistants, and therapy staff by appropriate mix of time as well as training level, especially since most nursing homes have no daily physician presence. More work needs to be done on quality-of-care measures, which rarely incorporate intrainstitutional quality factors such as inappropriate transfer of residents to hospitals. Other research priorities include such issues as the time required for carrying out basic nursing activities to deliver high-quality care, the relationship between nursing education and training on resident outcomes, and the relationship between caregiver wages and resident outcomes.

Ross, S.D., Sheinhair, I.A., Harrison, K.J., and others. (2000, June). "Systematic review and meta-analysis of the literature regarding the diagnosis of sleep apnea." (AHRQ contract 290-97-0016). Sleep 23, pp. 519-532.

These authors systematically reviewed the literature and did a meta-analysis of 249 relevant studies from 1980 through 1997 to develop an Evidence Report on the diagnosis of sleep apnea in adults. Sleep apnea is a 50 to 100 percent cessation of airflow during sleep, and may be responsible for 38,000 cardiovascular deaths per year and annual costs of $42 million for related hospitalizations. These authors found that the diversity of study designs and the objectives were very high, and the methodological rigor of these studies as assessments of diagnostic tests was very low. As a result, they cannot recommend standardization of diagnostic methodology for sleep apnea. Instead, they recommend that future research include standardization of terms and diagnostic criteria and consistently reported statistics to enhance the utility of studies on sleep apnea.

Editor's Note: Copies of AHRQ Evidence Report Number 1, Systematic Review of the Literature Regarding the Diagnosis of Sleep Apnea (AHRQ Publication No. 99-E002) and a summary (AHRQ Publication No. 99-E001) drawn from the report are available from the AHRQ Publications Clearinghouse. The report and summary were prepared for AHRQ under contract by MetaWorks, Inc., of Boston, MA.

Zhou, X-H., and Higgs, R.E. (2000). "Assessing the relative accuracies of two screening tests in the presence of verification bias." (AHRQ grant HS08559). Statistics in Medicine 19, pp. 1697-1705.

An ROC curve is commonly used to measure the accuracy of a medical test. It is a plot of the true positive fraction (sensitivity) against the false positive fraction (1-specificity) for increasingly stringent positivity criterion. Bias can occur when estimating an ROC curve if, for example, only some of the tested patients are selected for disease verification and if analysis is restricted only to the verified cases. This is known as verification bias. In this paper, the authors propose the use of two methods to construct confidence intervals for the difference in accuracy of two screening tests for dementia—an initial screening instrument and a more extensive followup clinical assessment for selected patients. They illustrate the application of the proposed methods to a simulated data set from an actual two-stage study of dementia that motivated the present research.

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Current as of August 2000
AHRQ Publication No. 00-0051

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