Clinical pharmacy interventions not only provide better patient care, but also can provide significant cost savings for the pharmacy. One of the most common interventions are renal dosing adjustments. Have you ever wondered how others are calculating creatinine clearance? I created a brief survey to find out. Ninety eight responses were complete enough to be included in this summary. The responses were fairly evenly spread across the number of practicing pharmacists and the number of beds within each facility.
Of the respondents, 74.23% indicated that the institution has an agreed upon methodology to calculate creatinine clearance. There was no significant difference when stratified by number of pharmacists or bed size. The range varied from 70 - 76% for number of practicing pharmacists and 69 - 81% for bed size.
Only 51.56% of pharmacists use the creatinine clearance calculation provided by their electronic medical record (EMR). Again, there was no significant difference when stratified by number of pharmacists or bed size. According to the results, a majority of pharmacists are not using more than one calculation for creatinine clearance when evaluating a patient; 60.42% respondents said that they only perform multiple calculations less than 10% of the time.
Cockcroft-Gault (CG) was the most commonly used renal dosing equation used in adults, as almost 75% of respondents used it the majority of the time: 48.94% of respondents reported using the equation every time and another 23.4% of respondents used it 91-99% of their time. In this survey, smaller facilities were most likely to use CG.
When respondents did not use CG as a renal dosing equation, they used the following equations:
For the 11 respondents that said other, their methods included using Hull, DuBois and eGFR, adjusting CG based on body weight, or rounding up serum creatinine.
The following graph shows when respondents used other calculations; the most common reasons were obesity and unstable renal function:
Those that responded “Other” have used CG when the manufacturer recommended another calculation, for breast cancer and carboplatin, and for patients with infections. A number of respondents that selected “Other” referenced body weight adjustments or indicated that they never make any adjustments to the standard CG calculation.
There was more variation in the responses regarding pediatric creatinine clearance calculations. The responses indicated that 25.64% use Schwartz every time and another 5.13% use the equation 91-99% for calculation. The revised Schwartz option was a clear leader as an alternate calculation, which was used by 49.02% of respondents.
There was a flaw in the survey design that caused a number of respondents to select “Other” for the pediatric calculation option, and then indicate that they did not treat pediatric patients or perform creatinine calculations for pediatrics. When those responses were removed, more than 80% of respondents used the Schwartz or revised Schwartz equations.