|
Quality of care and attributable healthcare costs in diabetic hypertensive patients initiated on calcium antagonist therapy |
Barron J J, Al-Zakwani I, Iarocci T |
|
|
Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology Two classes of calcium antagonists (CAs) for the treatment of diabetic hypertensive patients were examined. The classes were dihydropyridine calcium antagonists (DCAs) and non-dihydropyridine calcium antagonists (non-DCAs).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised patients aged 18 years and older with DM (Type 1 or 2) and hypertension.
Setting The setting was secondary care. The economic study was carried out in the USA.
Dates to which data relate The effectiveness and resource use data were gathered from July 1999 to May 2003. The prices reflected 2000-2002 values.
Source of effectiveness data The effectiveness evidence was derived from a single study.
Link between effectiveness and cost data The costing was carried out retrospectively on the same sample of patients as that used in the effectiveness study.
Study sample Power calculations were not performed. The patients were identified from an administrative claims database. A sample of 5,551 patients was identified, of which 1,515 were in the non-DC group and 4,036 in the DCA group. The patients in the non-DCA group had a mean age of 62 (+/- 12) years and 47% were male. The patients in the DCA group had a mean age of 62 (+/- 12) years and 53% were male. A random sample of patients was further selected from the providers who had the most frequent contacts with a given study patient. The sub-set comprised 313 patients (71 from the non-DCA group and 242 from the DCA group), whose baseline characteristics reflected the full population. Fifty-one non-DCA patients and 193 DCA patients had their blood pressure (BP) recorded before the first claim for CA. Sixty-two non-DCA patients and 219 DCA patients had their BP recorded after the first claim for CA. Forty-eight non-DCA patients and 183 DCA patients had their BP recorded both before and after the first claim for CA.
Study design This was a retrospective cohort study that was carried in several centres in the southwestern and western USA. The length of follow-up was not reported, but the patients were required to have complete data from at least 6 months before to 12 months after the first claim for a CA. No loss to follow-up was observed as only patients with complete data were included in the analysis.
Analysis of effectiveness All of the patients included in the initial study sample were accounted for in the effectiveness analysis. The primary outcome measure used was the change in BP in the before and after phases of the study. In addition, the proportion of patients having renal function evaluated was estimated. The study groups differed at baseline in that there was a significantly lower proportion of men in the non-DCA group, and non-DCA patients were less likely to have dyslipidaemia, peripheral vascular disease and nephropathy.
Effectiveness results In the pre-index period, the average systolic BP was 145.7 mmHg (95% confidence interval, CI: 141 - 150.7) in the non-DCA group and 149.9 mmHg (95% CI: 147.4 - 152.4) in the DCA group.
In the post-index period, the average systolic BP was 138.9 mmHg (95% CI: 135.1 - 142.8) in the non-DCA group and 139.5 mmHg (95% CI: 137.5 - 141.5) in the DCA group.
The mean change in systolic BP was -8 (+/- 13.2) mmHg in the non-DCA group and -9.8 (+/- 17.2) mmHg in the DCA group.
In the pre-index period, the average diastolic BP was 83.7 mmHg (95% CI: 81.1 - 86.4) in the non-DCA group and 86.1 mmHg (95% CI: 84.6 - 87.7) in the DCA group.
In the post-index period, the average diastolic BP was 79.2 mmHg (95% CI: 77.3 - 81.3) in the non-DCA group and 79.8 mmHg (95% CI: 78.6 - 81.1) in the DCA group.
The mean change in diastolic BP was -4.9 (+/- 7) mmHg in the non-DCA group and -5.9 (+/- 8.6) mmHg in the DCA group.
In the pre-index period, the proportion of patients achieving a mean systolic/diastolic BP less than 130/80 mmHg (BP goal) was 13.7% in the non-DCA group and 6.7% in the DCA group. The corresponding figures in the post-index period were 29% (non-DCA group) and 20.1% (DCA group), respectively.
None of the differences between the groups reached statistical significance.
With respect to renal function monitoring, in the whole sample, screening of urinary protein excretion was performed in less than 45% of patients over a 2-year period, serum creatinine values were detected in the records of 68.1% of patients, BP values were captured for about 94% of patients, and 46% of patients had undergone a test for microalbuminuria or other urinary protein.
Clinical conclusions The effectiveness analysis showed that the two CAs were equally effective in terms of changes in BP.
Measure of benefits used in the economic analysis No summary benefit measure was used because the effectiveness analysis showed that the two treatments were equally effective. In effect, a cost-minimisation analysis was carried out.
Direct costs Discounting was not relevant because the costs were incurred during a 2-year period. The unit costs were not presented separately from the quantities of resources used. A detailed breakdown of the cost items was not provided. All the costs attributable to hypertension and/or DM were considered in the analysis, including all services for glucose-lowering and antihypertensive drugs, and all services associated with hypertension or DM (i.e. office visits, emergency room visits, inpatient hospital admissions, and diagnostic laboratory testing). The cost/resource boundary of the health plan was adopted. The costs and resource use data were derived from the administrative claims database for the period 2000-2002. The price year was not explicitly reported.
Statistical analysis of costs The costs were presented using descriptive statistics (mean, median and CI). The costs were analysed using regression a analysis, which considered potential determinants such as prior attributable costs, age, gender and co-morbidities.
Indirect Costs The indirect costs were not included in the economic evaluation.
Sensitivity analysis No sensitivity analysis was performed.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results The use of concomitant medications showed that a significantly higher proportion of non-DCA patients were prescribed CA monotherapy in comparison with DCA patients. Further, DCA patients were significantly more likely to receive a combination therapy that included an angiotensin-converting enzyme inhibitor or a beta-blocker. However, DCA patients were less likely to receive combination therapy with diuretics.
The mean (adjusted) total attributable costs per patient per year were $1,637 (95% CI: 1,479 - 1,813; median unadjusted $840; absolute range: 0 - 110,661) in the non-DCA group and $1,989 (95% CI: 1,823 - 2,170; median unadjusted $981; absolute range: 0 - 206,339) in the DCA group, (p=0.004).
Synthesis of costs and benefits A synthesis of the costs and benefits was not relevant since a cost-minimisation analysis was carried out.
Authors' conclusions There were three main findings. First, antihypertensive treatments using non-dihydropyridine calcium antagonists (non-DCA) were associated with lower annual attributable costs than those including dihydropyridine calcium antagonists (DCA). Second, the decrease in blood pressure (BP) was statistically the same, regardless of which CA was used. Third, most patients were not treated to recommended BP goals and were not monitored adequately.
CRD COMMENTARY - Selection of comparators The selection of the comparators reflected actual prescribing patterns in the large health plan that was used to provide the data. You should decide whether they are valid comparators in your own setting.
Validity of estimate of measure of effectiveness The effectiveness evidence came from a retrospective observational study, which was based on a review of patients' charts. The clinical evidence came from a small sub-group of patients initially identified. Consequently, the study was likely to have been underpowered to detect statistically significant differences in the outcome measures. Further, the study groups were not comparable at baseline. The allocation of the patients to the study groups was not randomised. Thus, selection bias and confounding factors could have affected the results of the analysis. These issues tend to limit the internal validity of the analysis. The clinical outcome used in the study represented an intermediate measure of the effect of the interventions on the patients' health. Compliance with medication was not investigated.
Validity of estimate of measure of benefit No summary benefit measure was used in the analysis because a cost-minimisation analysis was conducted. Please refer to the comments in the 'Validity of estimate of measure of effectiveness' field (above).
Validity of estimate of costs The perspective of the study was that of the health plan. Therefore, only the direct medical costs were considered. Limited information on the cost analysis was provided. The unit costs and the quantities of resources used were not reported, and a detailed breakdown of the cost items was not given. This reduces the possibility of replicating the study. The source of the data was reported. It was unclear whether charges were used as proxies for costs since the economic estimates came from an administrative claims database. The costs were gathered during the period 2000-2002, but the price year was not explicitly reported.
Other issues The authors stated that their findings confirmed those observed in a published systematic review. However, further comparisons were not made. The issue of the generalisability of the study results to other settings was not addressed and sensitivity analyses were not performed. Consequently, the external validity of the study was low. The analysis referred to hypertensive patients with DM and this was reflected in the authors' conclusions.
Implications of the study The study results suggested that opportunities exist to improve the quality of care delivered to hypertensive patients with DM. The authors noted that large randomised clinical trials should be carried out to better examine the clinical and economic impact of CAs.
Source of funding Funded by Abbott Laboratories.
Bibliographic details Barron J J, Al-Zakwani I, Iarocci T. Quality of care and attributable healthcare costs in diabetic hypertensive patients initiated on calcium antagonist therapy. Clinical Drug Investigation 2004; 24(11): 641-649 Other publications of related interest Bakris GL, Weir MR, Secic M, et al. Differential effects of calcium antagonist subclasses on markers of nephropathy progression. Kidney International 2004;65:1991-2002.
Saydah SH, Fradkin J, Cowie CC. Poor control of risk factors for vascular disease among adults with previously diagnosed diabetes. JAMA 2004;291:335-42.
Chobanian AV, Bakris GL, Black HR, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA 2003;289:2560-72.
Indexing Status Subject indexing assigned by CRD MeSH Antihypertensive Agents /therapeutic use; Calcium Channel Blockers; Cost-Benefit Analysis; Diabetes Mellitus /blood /epidemiology /etiology; Health Care Costs AccessionNumber 22004009299 Date bibliographic record published 31/07/2005 Date abstract record published 31/07/2005 |
|
|
|