NextDose: A web-based Bayesian dose forecasting tool

Last updated 16 June 2024

Observation Types

The NextDose Doses and Observations window is used to enter doses and individual observations such as weight. Observation types such as weight are associated with a date and time so that time varying changes in these observations may be used by the NextDose model. When MIC is used as an observation it is treated as a time varying observation. The new MIC value will be applied to observed doses and concentrations from the time of the MIC observation.

There are also observation types that are not time sensitive. They can be associated with any date and time and have an effect across the full time sensitive dosing and observation history.

AUC Occ

The AUC Occ observation calculates the area under the curve (~AUC) after each dose until the time of the next dose (a dosing occasion) based on the predicted individual concentration shown in the graph on the Results page. Because this AUC is obtained by numerical integration it is an approximation to the actual AUC. It has the ~ prefix to signal this is an approximation. The ~AUC following the last dose is calculated until the end of the predicted individual concentration display. The measurement box should be set to a value of 1 to activate this observation type.

The AUC for each dose and associated individual CL/F value is displayed as AUC inf alongside the ~AUC occ value. The ratio of ~AUC occ to AUC inf gives an indication of how close ~AUC occ is approaching the steady state AUC during the dosing occasion.

AUC T1

The AUC T1 observation calculates the area under the curve (~AUC) of the predicted individual concentration from the AUC starting time (h) entered in the measured value box. If the starting time is set to “.” the value will be calculated from the date and time of the observation. The time in hours is counted from the time of the first observation (dependent variable) or dose in the Doses and Observations window.

AUC T2

The AUC T2 observation calculates ~AUC from the AUC starting time in AUC T1 and ending at the time entered in the AUC T2 measured value box. If the starting time is set to “.” the value will be calculated from the date and time of the AUC T1 or AUC T2 observation. The time of AUC T2 should be set to a value greater than AUC T1, otherwise no value for AUC is generated. Multiple pairs if AUC T1 and AUC T2 may be specified. If an AUC T1 value is specified without an accompanying AUC T2 then ~AUC will be calculated up to the time of the last predicted concentration shown on the Results graph.

Hint: Use AUC occ to see the hours of doses as a guide for selection of AUC T1 and AUC T2. Both AUC occ and AUC T1 and AUC T2 observations may be used at the same time.

Note: The AUC estimates calculated from the predicted individual concentration time course use a simple integration method with an error of around 5%.