I came across with this study here, https://www.clinexprheumatol.org/abstract.asp?a=5066
And this study says: "The sample size calculation was done to compare two different MTX starting dose regimens, based on a study investigating the pharmacokinetics of 25 mg of methotrexate (22) assuming a 67% higher MTX level in the accelerated dose regime and a dose-proportional bioavailability. We calculated that 9 patients in each dosing group will be sufficient to detect the expected difference in the pharmacokinetics of methotrexate (α=0.05, β=0.80)."
Any idea of what formula that they are using to come up with the 9 sample size?
it depends on your hypothesis, how big do you anticipate a difference will be ? this difference should at best be of clinical relevance, so that if the study is negative, that we have learned that this covariate is not of clinical relevance ?
Karel Allegaert - Thank you for your reply. I just want to know the way that the authors in this study ( https://www.clinexprheumatol.org/abstract.asp?a=5066 ) calculated the sample size. Because they did not show their work in the paper. I think the way they used could help me to calculate the sample size that I need for my study.
Karel Allegaert - my study is to detect the difference in bioactive form of methotrexate, methotrexate polyglutamate, between patients who are using methotrexate with different dosing frequencies (eg: fortnightly, 3-weekly and 4-weekly) and patients who are using standard dosing frequency, which is once weekly. But there are not many studies out there for me to be based on. So, I wonder how I should calculate the sample size to test the following hypothesis:
Null hypothesis (Ho): The extended-interval MTX dosing (once fortnightly dosing, once every three weeks dosing or once every four weeks dosing) will result in the different systemic exposure as current once weekly dosing of MTX. The extended-interval MTX dosing has different tolerability as current once weekly dosing of MTX.
Alternative hypothesis (Ha): The extended-interval MTX dosing (once fortnightly dosing, once every three weeks dosing or once every four weeks dosing) will result in the similar systemic exposure as current once weekly dosing of MTX. The extended-interval MTX dosing has similar tolerability as current once weekly dosing of MTX.
- Badges
- Science topic
- Similar topics
- Clinical Pharmacology
- Dosing