This is a feature that I have wanted to add to my PK programs for quite sometime. In the real world doses don’t get hung on time and dosages get changed before levels are drawn.
Complex is the keyword. This was incredibly complex to code, both the logic of data entry and analysis. It has taken weeks of intense work to complete. Currently in the testing phase, I hope to bring it to production soon.
When you select “Complex non-steady-state analysis” the program displays two grids, one for entering doses and the other for serum levels.
You may enter up to five doses of various amounts, given at different rates and at different times. You may enter up to two serum levels. Of course there are limitations (which the data entry routines catch). For example, you cannot enter a date/time for a level that conflicts with a dose date/time.
If the first serum level is drawn before the first dose it will be considered a baseline level. This is also something that I have wanted to add for years. It will be most useful when performing a follow-up pk consult on a long-term patient.
You will still see Bayesian fails. This new data entry methodology will not prevent them from happening. That is the nature of Bayesian and the highly variable nature of Vancomycin kinetics.
Even people who have used my programs for years fail to comprehend what Bayesian analysis involves. The first thing to realize is that Bayesian analysis begins with your population model. It then attempts to fit your measured levels to incremental variations of your population model. In classic Bayesian, if the data cannot be fitted to the model within reasonable statistical limits, then the data is thrown out. I do not believe that rule should be applied to clinical pharmacokinetics. So I leave it up to you to decide how to proceed by showing the “Bayesian analysis failed” dialog.
Essentially this dialog is telling you that your measured level differs too much from the model predicted level. You can find out what level the population model predicted by visiting the prospective tab. If you measured 6 but the model predicted 24, then never the twain shall meet. Either (1) you have chosen the wrong model for your patient, or (2) the measured level is wrong. That is your decision, not one to be made by a computer program, period.