Understanding Antihypertensive Medication Use after Living Kidney Donation through Linked National Registry and Pharmacy Claims Data

We describe factors associated with immunosuppression compliance after kidney transplantation and examine relationships between compliance with allograft outcomes and costs. Medicare claims for immunosuppression in 15 525 renal transplant recipients with at least 1 year of graft function were used to calculate compliance as medication possession ratio. Compliance was categorized by quartiles as poor, fair, good and excellent. We modeled adjusted associations of clinical factors with the likelihood of persistent compliance by multiple logistic regressions (aOR), and estimated associations of compliance with subsequent graft and patient survival with Cox proportional hazards (aHR). Adolescent recipients aged 19-24 years were more likely to be persistently noncompliant compared to patients aged 24-44 years (aOR 1.49 [1.06-2.10]). Poor (aHR 1.80 [1.52-2.13]) and fair (aHR 1.63[1.37-1.93]) compliant recipients were associated with increased risks of allograft loss compared to the excellent compliant recipients. Persistent low compliance was associated with a $12 840 increase in individual 3-year medical costs. Immunosuppression medication possession ratios indicative of less than the highest quartile of compliance predicted increased risk of graft loss and elevated costs. These findings suggest that interventions to improve medication compliance among kidney transplant recipients should emphasize the benefits of maximal compliance, rather than discourage low compliance.

The validity of drug exposure measurement based on pharmacy records was investigated taking into account completeness of data, drug compliance, and different methods of drug exposure measurement in pharmacy records. Data on prescription drug use were collected from home inventories and community pharmacies in a survey on drug use and compliance in 115 elderly people. To compare drug exposure in pharmacy records with exposure in the home inventory, three different methods for exposure measurement in pharmacy records were used. Two employed a fixed time window of 30 and 90 days, respectively, and the third method was based on the calculated duration of use of a prescription ("legend time"). Drug exposure in the home inventory was taken as the gold standard and sensitivity, specificity, and positive predictive values of the different methods were calculated for the most frequently used drugs and drug categories. The specificity and positive predictive value of all three methods was generally high (0.93-1.00 and 0.67-1.00, respectively). The 90-day fixed method and the legend time method generally showed high sensitivity (range: 0.67-1.00 and 0.63-0.83, respectively) for drugs that were used on a chronic basis, while the 30-day fixed method had poor sensitivity (range: 0.29-0.69). Drugs that were used according to the home inventory but not according to the pharmacy records methods could be almost completely retrieved in the pharmacy records of a one-year period showing that these records were virtually complete with regard to prescription drugs. We conclude that computerized pharmacy records can be a reliable source of the true drug exposure as estimated in a home inventory, when adequate attention is paid to the definition of the exposure time-window and when these records are comprehensive with regard to prescription drugs.

Data regarding health outcomes among living kidney donors are lacking, especially among nonwhite persons. We linked identifiers from the Organ Procurement and Transplantation Network (OPTN) with administrative data of a private U.S. health insurer and performed a retrospective study of 4650 persons who had been living kidney donors from October 1987 through July 2007 and who had post-donation nephrectomy benefits with this insurer at some point from 2000 through 2007. We ascertained post-nephrectomy medical diagnoses and conditions requiring medical treatment from billing claims. Cox regression analyses with left and right censoring to account for observed periods of insurance benefits were used to estimate absolute prevalence and prevalence ratios for diagnoses after nephrectomy. We then compared prevalence patterns with those in the 2005-2006 National Health and Nutrition Examination Survey (NHANES) for the general population. Among the donors, 76.3% were white, 13.1% black, 8.2% Hispanic, and 2.4% another race or ethnic group. The median time from donation to the end of insurance benefits was 7.7 years. After kidney donation, black donors, as compared with white donors, had an increased risk of hypertension (adjusted hazard ratio, 1.52; 95% confidence interval [CI], 1.23 to 1.88), diabetes mellitus requiring drug therapy (adjusted hazard ratio, 2.31; 95% CI, 1.33 to 3.98), and chronic kidney disease (adjusted hazard ratio, 2.32; 95% CI, 1.48 to 3.62); findings were similar for Hispanic donors. The absolute prevalence of diabetes among all donors did not exceed that in the general population, but the prevalence of hypertension exceeded NHANES estimates in some subgroups. End-stage renal disease was identified in less than 1% of donors but was more common among black donors than among white donors. As in the general U.S. population, racial disparities in medical conditions occur among living kidney donors. Increased attention to health outcomes among demographically diverse kidney donors is needed. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others.)