Discrete event simulation of patient admissions to a neurovascular unit.

Evidence exists that clinical outcomes improve for stroke patients admitted to specialized Stroke Units. The Toronto Western Hospital created a Neurovascular Unit (NVU) using beds from general internal medicine, Neurology and Neurosurgery to care for patients with stroke and acute neurovascular conditions. Using patient-level data for NVU-eligible patients, a discrete event simulation was created to study changes in patient flow and length of stay pre- and post-NVU implementation. Varying patient volumes and resources were tested to determine the ideal number of beds under various conditions. In the first year of operation, the NVU admitted 507 patients, over 66% of NVU-eligible patient volumes. With the introduction of the NVU, length of stay decreased by around 8%. Scenario testing showed that the current level of 20 beds is sufficient for accommodating the current demand and would continue to be sufficient with an increase in demand of up to 20%.

Assessment of tinnitus: measurement of treatment outcomes.

There is a wide range of assessment techniques for tinnitus, but no consensus has developed concerning how best to measure either the presenting features of tinnitus or the effects of tinnitus treatments. Standardization of reliable and valid tinnitus measures would provide many advantages including improving the uniformity of diagnostic and screening criteria between clinics and facilitating comparison of treatment outcomes obtained at different sites. This chapter attempts to clarify issues involved in developing self-report questionnaires for the assessment of tinnitus. While the tinnitus questionnaires that are currently available provide valuable information on which to base diagnostic and screening decisions, they were not originally developed in such a way as to maximize their sensitivity to treatment-related changes in tinnitus. As a result, their construct validity for measuring treatment benefit has not received appropriate attention. In this paper, special emphasis is devoted to the use of effect sizes as an estimate of the ability of questionnaires (and their individual items) to measure changes associated with treatment. We discuss the criteria relevant to evaluating the effectiveness of a questionnaire for diagnostic purposes vs. for treatment-evaluation purposes, and we present a detailed illustration of how the various criteria have been applied in a recent questionnaire development effort.

Measuring hearing aid benefit using a willingness-to-pay approach.

The value associated with self-perceived hearing aid benefit was assessed using a "willingness-to-pay" (WTP) approach. Abbreviated Profile of Hearing Aid Benefit (APHAB) data were obtained from 79 veterans who also indicated how much they were willing to pay for each hearing aid. The results of a multiple regression analysis revealed that veterans were willing to pay $22.06 more for a hearing aid for each 1-point increase in APHAB global benefit. A second multiple regression analysis revealed that the APHAB subscale scores for Ease of Communication (EC) benefit and understanding speech in Background Noise (BN) benefit, as well as income level, were all significant predictors of WTP. In addition, each 1-point increase in EC, BN, and Reverberation benefit increased the value associated with amplification by $16.32, $16.88, and $13.78, respectively. Each 1-point increase in the Aversiveness of Sounds subscale decreased the value associated with amplification by $7.63. The mean WTP across all income groups was $981.71 per hearing aid. These data are interpreted to support the use of WTP as a valid measure of hearing aid benefit.

The effects of intervention strategy on self-perception of hearing handicap.

The purpose of this study was to determine whether participation in a counseling-based aural rehabilitation program would result in greater reduction of self-perceived hearing handicap than hearing aid use alone. Thirty-one postlingually hearing-impaired adults were placed into three groups after audiological evaluation. The first group received hearing aids and participated in a counseling-based aural rehabilitation (AR) program. The second group received hearing aids only. The third group received neither hearing aids nor counseling-based AR. The Hearing Handicap Inventory for the Elderly was administered to all subjects before audiological evaluation and again to all subjects 2 mo after receipt of hearing aids for the experimental groups. For both experimental groups, self-perception of hearing handicap was significantly reduced as a function of intervention when measured on any of the three Hearing Handicap Inventory for the Elderly scales, whereas there was no change in self-perception of hearing handicap for the control group on any scale. In addition, there was weak but significant evidence that participating in the counseling-based AR program in addition to hearing aid use resulted in a greater reduction of self-perceived hearing handicap than did hearing aid use alone.

Unintentional self-intoxication with inorganic calcium.

A 40-year-old woman with previous parathyroidectomy for adenoma was found to have a serum calcium level of 5.35 mmol l-1 (21.4 mg dl-1). Inadvertent calcium overdose had occurred because of her mistaken belief that if some prescribed calcium was good, then more was better. Her misconception is in contrast with that of patients with Münchausen's syndrome, who deliberately made themselves hypercalcaemic by ingesting calcium or Vitamin D surreptitiously. Inorganic calcium is increasingly promoted for its presumed, though unproven, effectiveness in prevention and treatment of osteoporosis. Massive overdose can be associated with serious risks, as illustrated by the present case, which we believe represents the highest serum calcium level yet reported in an ambulatory patient.

Is there a role for surgery in the acute management of infective endocarditis? A decision analysis and medical claims database approach.

In the absence of good clinical evidence from a randomized trial, the authors performed a decision analysis to determine the potential value of early elective surgery (OPNOW) for patients with left-sided Staphylococcus aureus infective endocarditis. Initial impressions (before performance of decision analysis) and initial runs at the formal models using probability estimates derived from clinicians suggested that OPNOW (i.e., within a few days of starting antibiotics) offered no advantage over attempted medical cure (WAIT) (life expectancy: WAIT = 325 weeks; OPNOW = 255 weeks). Extensive sensitivity analyses identified critical variables that needed further empirical estimation. The Manitoba Health Services Commission database identified 127 incident cases of endocarditis between April 1, 1979, and March 31, 1985, enabling estimation of values for these critical variables. With these estimates, the early surgery strategy appeared much better than the previous analyses had suggested (life expectancy: WAIT = 208 weeks, OPNOW = 256 weeks). The authors believe that this approach of combining decision analysis with medical claims databases is useful as an alternative or precursor to randomized trials, especially where the resource requirements and logistic difficulties of performing randomized trials are great.

What's wrong with decision analysis? Can the left brain influence the right?

In order to gain insight into the impact that decision analysis has had on clinical practice, we presented a published report on the utility of renal biopsy for patients with idiopathic nephrotic syndrome to a group of nephrologists and residents at a teaching hospital. Although the analysis showed that the decision to biopsy or use empiric steroids without biopsy was a toss-up in terms of patient outcomes, only one of six staff nephrologists was willing to forego the biopsy strategy. Many clinicians in the group discussed the pure value of the information (e.g in making statements about prognosis) derived from the biopsy as an important factor in the choice of clinical strategies, a characteristic which was not captured by the published analysis. Also, some clinicians were uncomfortable with the entire simulation process as there were no "real patients" in the study. It appeared that clinical intuition based on pattern recognition could not be influenced by the linear logic of decision analysis. We suggest that major challenges for decision analysts include incorporating the value of information into analyses, selecting and cultivating the most appropriate clinical audience, and demonstrating the benefits of decision analysis for either the decision-making process or health outcomes. Without meeting these challenges, decision analysis may remain an esoteric field within academic medicine, which will continue to have limited impact on clinical practice.

Cardiac assessment for patients undergoing noncardiac surgery. A multifactorial clinical risk index.

In this article, we describe a multifactorial cardiac risk index that can be used to assess patients undergoing noncardiac surgery. The index is a modified version of an index that was previously generated by Goldman and coworkers on a set of 1001 consecutive patients and prospectively validated in our clinical setting (a general medical consultation service in a large teaching hospital) on 455 patients. We present a Bayesian approach to assessing cardiac risks by converting average risks for patients undergoing particular surgical procedures (pretest probabilities) to average risks for patients with each index score (posttest probabilities). A simple nomogram is presented for performing such a calculation.

Predicting cardiac complications in patients undergoing non-cardiac surgery.

The authors prospectively studied 455 consecutive patients referred to the general medical consultation service for cardiac risk assessment prior to non-cardiac surgery, in order to validate a previously derived multifactorial index in their clinical setting. They also tested a version of the index that they had modified to reflect factors they believed to be important. For patients undergoing major surgery, the original index performed less well in the validation data set than in the original derivation set (p less than 0.05), but still added predictive information to a statistically significant degree (p less than 0.05). The modified index also added predictive information for patients undergoing both major and minor surgery, demonstrating an area under the Receiver Operating Characteristic curve of 0.75 (95% confidence interval of 0.70 to 0.80). A simple nomogram is presented which will enable conversion of pretest probabilities into posttest probabilities using the likelihood ratios associated with each risk score. It is recommended that clinicians estimate local overall complication rates (pretest probabilities) for the clinically relevant populations in their settings before they apply the predictive properties (likelihood ratios) demonstrated in this study in order to calculate cardiac risks for individual patients (posttest probabilities).

Do interns and residents order more tests than attending staff? Results of a house staff strike.

Between October 30 and November 5, 1980, the Professional Association of Interns and Residents of Ontario called a strike of house staff in Ontario's teaching hospitals. The authors obtained data concerning utilization of laboratory tests and radiology procedures during that period and for the same days 2 weeks before and after the strike. During the strike period, the number of tests performed per patient day decreased by only 8.3%. After accounting for proportional changes in emergency and nonemergency admissions, there was no significant change in the number of tests or relative value units performed per patient day as a result of the strike. These results suggest that the volume of tests performed in teaching hospitals is more likely related to the case mix and severity of illness of patients admitted to these institutions than to a pure "teaching effect."

Quality of life of patients on long-term total parenteral nutrition at home.

Quality of life and quality-adjusted survival were measured for a cohort of 73 patients maintained on long-term parenteral nutrition at home (HPN) for periods ranging from six months to 12 years. Quality-adjusted survival was also modeled (although not directly observed) for this cohort under alternative therapeutic strategies (e.g., parenteral nutrition in hospital as needed). Using three utility assessment techniques (category scaling, time-tradeoff, direct questioning of objectives), quality of life was measured through interviews with 37 patients. The quality of life of the patients interviewed was good (mean value 0.73 where 0 represents death and 1.0 represents perfect health); for those who had experienced a period of chronic malnutrition before HPN, quality of life had improved. For the entire cohort, the estimate of quality-adjusted survival was four times greater with HPN than with the alternative therapeutic strategies (p less than 0.001). In comparison with alternative strategies, HPN significantly improves the quality of life of patients unable to sustain themselves with oral alimentation. Quality of life (utility) techniques can be used to evaluate the effectiveness of interventions for patients with chronic diseases.

A cost-utility analysis of the home parenteral nutrition program at Toronto General Hospital: 1970-1982.

We performed an economic evaluation of a home parenteral nutrition (HPN) program by measuring the incremental costs and health outcomes for a cohort of 73 patients treated at our institution from November 1970 to July 1982. Over a 12-year time frame, we estimate that HPN resulted in a net savings in health care cost of $19,232 per patient and an increase in survival, adjusted for quality of life, of 3.3 years, compared with the alternative of treating these patients in hospital with intermittent nutritional support when needed. This result was sensitive to assumptions made about the cost of the alternative treatment strategy. When these assumptions were most unfavorable to the HPN program, we estimated that HPN resulted in incremental costs of $48,180 over 12 years, $14,600 per quality-adjusted life-year gained. We conclude that the cost-utility of HPN compares favorably with other health care programs, when HPN is used to treat patients with gut failure secondary to conditions such as Crohn's disease or acute volvulus. Since only one patient with active malignancy was enrolled in our HPN program, these results should not be extrapolated to patients with active malignancy.