An economic evaluation of patch testing in the diagnosis and management of allergic contact dermatitis.

BACKGROUND: A previous retrospective study indicated that patch testing is cost-effective and well accepted by patients. OBJECTIVE: The objective of this observational prospective study was to show the cost-effectiveness of patch testing in patients suspected of allergic contact dermatitis (ACD) and to determine the order in which different severity groups rank in terms of cost-effectiveness. METHODS: This observational study was conducted in 567 patients from 10 investigator sites over a period of 1 year. All patients with a suspicion of contact allergy who exhibited at least moderate disease activity were included in the study and were stratified according to disease severity and whether or not they were patch tested. In each severity category, the cost-effectiveness of patch testing was evaluated. Patients who were ruled out for contact allergy by the first 6 months after admission were excluded. A validated dermatology-specific quality of life instrument was administered to all the patients at entrance into the study and at 6 and 12 months after that. The cost-effectiveness analysis is shown using a decision analysis model. RESULTS: Patch testing was performed on 22% of patients with mild disease, 41% of patients with moderate disease, and 50% of patients with severe disease. As a result of changes made in their lifestyle, 66% in the patch-tested group and 51% in the non-patch-tested group reported 75% or more improvement in disease symptoms after 6 months. Early confirmation of diagnosis helped reduce the prediagnosis costs of treatment, which was mostly based on preliminary diagnosis. The greatest quality of life benefits from patch testing, relative to no patch testing, occurred in subjects with recurrent or chronic ACD. CONCLUSION: Patch testing is most cost-effective and reduces the cost of therapy in patients with severe ACD.

Practical issues in conducting pharmacoeconomic studies.

Many difficulties are inherent to pharmacoeconomic studies. Because these studies are observational, there are many factors that cannot be controlled; for example, there are many variations across the country in the practice of any particular therapy. Therefore, designing a case report form that will match the source documents from various investigator sites is not easy. Issues arise in every activity such as choice of investigator site, data collection, data analysis, and interpretation of the results. These issues will be discussed, and an example of a pharmacoeconomic study conducted to evaluate the cost-effectiveness of patch testing in patients diagnosed with allergic contact dermatitis will be presented.

A retrospective evaluation of patch testing in patients diagnosed with allergic contact dermatitis.

One reason given by clinicians for not using patch testing in patients with dermatitis is that it may not improve the treatment outcome. The main objectives of this retrospective study were to determine the frequency of use of patch testing as an aid to the diagnosis of allergic contact dermatitis (ACD), to determine the ACD-related costs before and after diagnosis of the disease, and to determine the benefit of the diagnosis of ACD, with or without patch testing, to the patient's treatment outcome. This study will also provide definite direction for a prospective outcome study. Medical records of 270 patients with ACD were utilized retrospectively to study the benefit of patch testing. Patch testing was performed on 56 percent of these patients. Patch testing was found to bring about a larger decrease in the disease severity index and percentage disease activity from prediagnosis to postdiagnosis than diagnosis without patch testing. In the group of patients with a prediagnosis disease duration of two months to one year, the postdiagnosis duration was considerably less for those patch tested and treated than those that were treated without patch testing. Patch testing was found to be the most cost-effective in patients with a disease duration of two months to one year.

Kinetics of cefsulodin in patients with renal impairment.

Kinetics of cefsulodin were determined after administration of a 500-mg dose to normal subjects and patients with various degrees of renal insufficiency, including those requiring hemodialysis. Elimination kinetics were described by a two-compartment model. The steady-state volume of distribution was 0.26 liters/kg regardless of renal function. When the glomerular filtration rate (GFR) was greater than 80 ml/min, the elimination half-life (t1/2) was 1.9 hr. When the GFR ranged from 79 to 53 ml/min, t1/2 was 2.9 hr. In patients with moderate renal failure, in whom the GFR was 32-22 ml/min, t1/2 was 5.7 hr. In anuric patients, t1/2 was 13.0 hr. During hemodialysis the average plasma flow was 122 ml/min, dialyzer plasma clearance was 50.9 ml/min, concentration of drug in plasma was reduced by 60%, and t1/2 decreased to 2.1 hr. After dialysis the elimination rate appeared to return to that found in subjects not undergoing dialysis. While progressive renal failure slows the elimination of cefsulodin, there is a linear relationship between elimination of cefsulodin and GFR such that dosage nomograms can be developed. In patients undergoing hemodialysis, the maintenance dose of cefsulodin should be reduced to 10% of normal, and 60% of the dose should be given after hemodialysis.

Upper extremity prone position exercise as aerobic capacity indicator.

Peak oxygen uptake of prone upper extremity exercise (VO2peak arm) compared with maximal oxygen uptake of upright lower extremity cycling (VO2max leg) was examined in an unselected young healthy male population (n = 21). The large standard deviation of the mean value of VO2peak arm expressed as a percentage of VO2max leg (60.48% +/- 11.84%) discourages use of a maximal upper extremity exercise test to predict total body aerobic capacity (r = 0.595 p = 0.002). However, the relationship between VO2peak arm and VO2max leg was influenced by the individual's cardiorespiratory fitness and capacity to perform either arm or leg work. When the population was divided into subgroups according to cardiorespiratory fitness or when subjects previously trained for either arm or leg work were excluded from analysis, the predictive power of VO2peak arm improved. (r = 0.946 p less than 0.001). Study results suggest that with careful analysis of subjects' fitness prior to upper extremity exercise testing, such exercise in a prone position can indicate aerobic capacity and may be used for fitness training when lower limb disabilities exist.

Cefsulodin kinetics in renal impairment.

Cefsulodin kinetics were determined after a 500-mg dose to normal subjects and patients with varying degrees of renal insufficiency, including those requiring hemodialysis. Elimination kinetics were described by a two-compartment model. Steady-state volume of distribution was 0.26 l/kg regardless of renal function. When glomerular filtration rate (GFR) was more than 80 ml/min, elimination half-life (t1/2) was 1.9 hr, total body clearance (ClT) was 2.01 ml/kg/min, and renal clearance (ClR) was 1.09 ml/kg/ in. When GFR ranged from 79 to 53 ml/min, t1/2 was 2.9 hr, ClT was 1.17 ml/kg/min, and ClR was 0.65 ml/kg/min. In subjects with moderate renal failure in whom GFR was 32 to 22 ml/min, t1/2 was 5.7 hr, Clt was 0.66 ml/kg/min, and ClR was 0.26 ml/kg/min. In anuric patients t1/2 was 13.0 hr. and ClT was 0.19 ml/kg/min or 9.5% of ClT in normal subjects. There was a linear relationship between ClT and GFR such that ClT = 0.19 + 0.017 GFR (r = 0.95). During hemodialysis the average plasma flow was 122 ml/min, dialyzer plasma clearance was 50.9 ml/min, plasma drug concentration was reduced by 60%, and t1/2 fell to 2.1 hr. After dialysis the elimination rate appeared to return to that in nondialysis studies. Therefore, renal failure reduces the ClT of cefsulodin. In hemodialysis patients the maintenance dose of cefsulodin should be reduced to 10% of normal and 60% of the dose should be given after hemodialysis.

Sympathetic influence on ventricular compliance.

Intracisternal injections of veratrine in the anesthetized dog were used to study the effects of extreme sympathetic stimulation on left ventricular diastolic compliance. The results obtained were compared with those seen during volume expansion with whole blood, and after removal of both stellate ganglia. The injection of veratrine into the cisterna magna caused an increase in left ventricular end-diastolic pressure (LVEDP) which was considerably larger than that which occurred in left ventricular end-diastolic circumferential (LVEDC) segment length suggesting a reduction in diastolic compliance. There were also increases in left ventricular systolic pressure (LVSP) as well as its first derivative (LV dp/dt). Bilateral stellectomy during the veratrine response abruptly reduced LVEDP with a lesser decrease in LVEDC. Thus, the left ventricular compliance change was reversed. Both LVSP and LV dp/dt were decreased by stellectomy but remained above control levels. During transfusion, the pressure-length curve of the ventricle was located downward and to the right in comparison with the curve observed with intracisternal veratrine.

Myocardial performance during hemorrhagic shock in the pancreatectomized dog.

Myocardial performance was evaluated in nine pancreatectomized and 12 nonpancreatectomized dogs by measuring left ventricular pressure (LVP), maximal dP/dt (max dP/dt), left ventricular end-diastolic pressure (LVEDP), pulmonary arterial pressure (PAP), aortic pressure (AoP), and lead II of the electrocardiogram during standardized hemorrhagic shock. Cardiac output (CO) and hematocrit were determined before hemorrhage, after 4 h of oligemia, when postinfusion mean blood pressure declined to 60 mmHg. Left ventricular function curves were obtained, by varying preload, in control dogs and 2 h after reinfusion of the shed blood in those dogs subjected to shock. Both groups of dogs showed identical responses to the shock procedure. In the immediate postinfusion period, LVP, max dP/dt, LVEDP, and mean blood pressure returned to near-control values, while PAP was significantly elevated. The postinfusion decline (after 60-90 min) in AoP was accompanied by a similar reduction in LVEDP. Left ventricular performance in hemorrhagic shock did not differ significantly from that seen in control dogs. In addition, there was no electrocardiographic indication of myocardial ischemia. The data indicate that terminal hemorrhagic shock need not be accompanied by myocardial depression whether or not the pancreas is intact.