Laboratory evaluation of potassium and creatinine among ambulatory patients prescribed spironolactone: are we monitoring for hyperkalemia?
BACKGROUND
Serum potassium and creatinine evaluation is recommended in patients prescribed spironolactone, yet the proportion of ambulatory patients chronically dispensed spironolactone receiving evaluation is not well understood.


OBJECTIVE
To estimate the rate of potassium and creatinine evaluation and identify factors associated with conducting these tests among ambulatory patients dispensed spironolactone.


METHODS
A retrospective cohort study was designed to evaluate patients at 10 health maintenance organizations with ongoing spironolactone dispensing for one year (N = 2257). Potassium and creatinine evaluation were determined from administrative data. Associations between patient characteristics and laboratory testing were assessed, using logistic regression modeling.


RESULTS
Serum creatinine and potassium were evaluated in 72.3% of patients during a 13 month period. The likelihood of potassium and creatinine monitoring was greater among patients who were older (OR 1.28; 95% CI 1.17 to 1.41 per decade of life); male (OR 1.25; 95% CI 1.01 to 1.54); had diabetes (OR 1.63; 95% CI 1.31 to 2.03); received concomitant therapy with angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (OR 2.23; 95% CI 1.74 to 2.87), potassium supplements (OR 1.96; 95% CI 1.51 to 2.54), or digoxin (OR 2.10 95% CI 1.48 to 2.98); or had more outpatient visits (OR 1.31; 95% CI 1.19 to 1.44). Among patients with heart failure (n = 790), factors associated with the incidence of laboratory testing were diabetes (OR 1.64, 95% CI 1.14 to 2.34), outpatient visits (OR 1.20; 95% CI 1.02 to 1.41), and digoxin therapy (OR 2.26; 95% CI 1.38 to 3.69).


CONCLUSIONS
Three-fourths of ambulatory patients dispensed spironolactone receive recommended laboratory evaluation, with monitoring more likely to be completed in patients prescribed concomitant therapy with drugs that increase hyperkalemia risk, older patients, and those with diabetes.
Raebel
Marsha A
MA
Kaiser Permanente Colorado Clinical Research Unit and School of Pharmacy, University of Colorado at Denver and Health Sciences Center, Denver, CO 80237, USA. Marsha.A.Raebel@kp.org
McClure
David L
DL
Chan
K Arnold
KA
Simon
Steven R
SR
Feldstein
Adrianne C
AC
Lafata
Jennifer Elston
JE
Andrade
Susan E
SE
Gunter
Margaret J
MJ
Nelson
Winnie W
WW
Roblin
Douglas
D
Platt
Richard
R
D000368:Aged; D000553:Ambulatory Care; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood*; D016903:Drug Monitoring; D005260:Female; D006801:Humans; D006947:Hyperkalemia / Q000097:blood / Q000139:chemically induced*; D008297:Male; D011188:Potassium / Q000097:blood*; D012189:Retrospective Studies; D013148:Spironolactone / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use
D013148:Spironolactone; D003404:Creatinine; D011188:Potassium