Willingness to pay for periodontal therapy: development and testing of an instrument

OBJECTIVES: The objective of this study was to develop and test the feasibility and validity of a willingness to pay (WTP) tool in a dental setting. METHODS: A questionnaire measured individuals' preferences among alternative treatments for periodontal disease and the maximum they would be willing to pay for their treatment of choice in terms of dental insurance premiums. The questionnaire provides detailed information, in probabilistic terms, of the risks and benefits of treatment choices for moderate to advanced adult periodontitis. It was pilot tested on 23 periodontal patients and 18 dental school faculty and staff. RESULTS: The majority (92.6%) felt the questionnaire was an accurate representation of treatments and outcomes, establishing face and content validity. In terms of construct validity, four hypotheses were tested: (1) manipulation of the outcomes of the preferred treatment led to a predictable shift in preferences for 38 subjects (92.7%); (2) although periodontal patients were not more likely to choose periodontal surgery than nonpatients (P = .14), those with a history of surgery were more likely to choose surgery again (P = .06); (3) WTP was positively related to income level (P = .05); and (4) subjects were willing to pay more for coverage for themselves than for others. Periodontal surgery was the preferred treatment for moderate to advanced periodontal disease, and was more strongly preferred than other choices (i.e., a higher WTP) for all income groups. The intraclass correlation coefficient for treatment preferences was 0.95 (P < .001) and the kappa for WTP was 0.78 (P < .001). CONCLUSION: This pilot study supports some of the criteria concerning validity of the WTP questionnaire to measure preferences for alternative periodontal therapies. Further testing on larger samples is required to confirm these results.     

Preference based measurements in dentistry: a review of the literature and recommendations for research

Clinical outcomes are used routinely in dental clinical practice to determine whether or not a patient has exhibited improvement following treatment. While these measures can be useful in comparing therapies in disease specific terms, they do not incorporate outcomes which may be of interest to patients. Preference based outcome measurements, on the other hand, take into account an individual's life style, overall well being and economic resources. There is a number of preference based measures available from the medical field, many of which have been adapted for use in a dental setting. This paper outlines the strengths and weaknesses of these preference based measures, using examples from the dental literature when available. Particular emphasis is placed on an economic tool known as contingent valuation or 'willingness to pay' as a potential technique in the measurement of dental preferences.     

Radioimmunoassay of human plasma retinol-binding protein

A radioimmunoassay for human plasma retinol-binding protein (RBP) has been developed utilizing a double antibody precipitation technique. RBP was purified 1500- to 2000-fold by procedures described previously. A specific anti-human RBP antiserum was prepared in rabbits by three once-weekly injections of purified RBP emulsified with Freund's adjuvant. RBP was iodinated with (131)I and the RBP-(131)I was purified by gel filtration on Sephadex G-100 after complex formation with human plasma prealbumin. The RBP-(131)I was completely (> 95%) immunoprecipitable in the presence of an excess of specific antiserum, it was not (< 5%) immunoprecipitable in the absence of specific antiserum, and it could be completely displaced from antibody by excess unlabeled RBP. The standard curve obtained in the immunoassay with normal plasma was identical to that with pure RBP. Duplicate samples differed from their mean by 5 +/-5% (+/-SD). There was a quantitative recovery of pure RBP added in varying amounts to normal plasma. The immunoassay accurately measured RBP in amounts of 10-100 ng per assay tube. There was no significant difference in the immunoreactivity of apo-RBP as compared to holo-RBP. The mean plasma values (+/-SEM) for a group of 76 normal subjects were 47.2 +/-1.6 mug/ml for males and 41.6 +/-1.6 mug/ml for females. Plasma RBP levels were markedly depressed (15 +/-2.3 mug/ml) in 14 patients with acute viral hepatitis. There was a highly significant correlation between the plasma levels of RBP and of vitamin A in both normal subjects and patients with hepatitis. In all subjects plasma RBP was generally saturated with retinol. The data suggest that under normal circumstances RBP circulates almost exclusively as the holoprotein.     

Outcomes in patients admitted for rehabilitation with spinal cord or cauda equina lesions following degenerative spinal stenosis

Purpose. To evaluate outcome measures and the factors affecting them in patients treated between 1962 and 2000 at Loewenstein Rehabilitation Hospital, Israel.

Method. This retrospective cohort study included 262 patients with spinal neurological lesions (spinal cord or cauda equina lesions) following degenerative spinal stenosis. Data were collected retrospectively. Survival was assessed using the Kaplan-Meier method and the relative mortality risk by the Cox model. Neurological recovery was evaluated by the change in Frankel grades, and factors that affect it were assessed by logistic regression. Associations of length of stay in rehabilitation were analyzed with ANOVA.

Results. Median age at lesion onset was 61 years and median survival 17.6 years. Age at spinal neurological lesion onset was found to be the only factor with a significant effect on survival. Of the 148 patients who had Frankel grades A, B, or C on admission, 58% achieved recovery to grades D and E. Frankel grade at admission, age, and spinal neurological level had a significant effect on recovery. The mean length of stay was 99.7 days, and only Frankel grade had a significant effect on length of stay.

Conclusions. Patients with spinal stenosis and disabling spinal neurological lesions can achieve significant neurological recovery and survive for many years. They require adequate care in a specialist rehabilitation system.     

Prevention of venous thromboembolism in medical patients with enoxaparin: a subgroup analysis of the MEDENOX study.

The Medical Patients with Enoxaparin (MEDENOX) trial was a randomized, placebo-controlled study that defined the risk of venous thromboembolism (VTE) in acutely ill, immobilized, general medical patients and the efficacy of the low-molecular-weight heparin, enoxaparin, in preventing thrombosis. We performed a post-hoc analysis to evaluate the effect of 40 mg enoxaparin once daily on MEDENOX patient outcome in different types of acute medical illness (heart failure, respiratory failure, infection, rheumatic disorder and inflammatory bowel disease) and pre-defined risk factors (chronic heart and chronic respiratory failure, age, immobility, previous VTE and cancer). The primary outcome was the occurrence of documented VTE between days 1 and 14. The relative risk reduction [95% confidence intervals (CI)] for VTE comparing 40 mg enoxaparin with placebo in the subgroups were: acute heart failure, 0.29 (95% CI, 0.10-0.84); acute respiratory failure, 0.25 (95% CI, 0.10-0.65); acute infectious disease, 0.28 (95% CI, 0.09-0.81); and acute rheumatic disorder, 0.48 (95% CI, 0.11-2.16). The relative risk reduction for VTE in the pre-defined risk factor subgroups were: chronic heart failure, 0.26 (95% CI, 0.08-0.92); chronic respiratory failure, 0.26 (95% CI, 0.10-0.68); age, 0.22 (95% CI, 0.09-0.51); immobility, 0.53 (95% CI, 0.14-1.72); previous VTE, 0.49 (95% CI, 0.15-1.68); and cancer, 0.50 (95%o CI, 0.14-1.72). The beneficial effects of enoxaparin extend to a wide range of acutely ill medical patients.