Loading…
An Extension of Janmahasatian’s Fat-Free Mass Model for Universal Application Across Populations of Different Ethnicities
Background Fat-free mass (FFM)-based dose scaling is increasingly being adopted in clinical pharmacology. Given the complexities with the measurement of FFM in clinical practice, choosing an appropriate equation for FFM is critical for accurate dose scaling. Janmahasatian’s FFM model (FFM Jan ) has...
Saved in:
Published in: | Clinical pharmacokinetics 2020-09, Vol.59 (9), p.1161-1170 |
---|---|
Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | Background
Fat-free mass (FFM)-based dose scaling is increasingly being adopted in clinical pharmacology. Given the complexities with the measurement of FFM in clinical practice, choosing an appropriate equation for FFM is critical for accurate dose scaling. Janmahasatian’s FFM model (FFM
Jan
) has largely remained the preferred choice because of its mechanistic basis and good predictive properties. This model was, however, developed from a largely European cohort and has been shown to give biased predictions of FFM in Indian people.
Objective
The objective of this work was to derive an extended version of the FFM
Jan
model (FFM
Ext
) that accounts for the variation in body composition due to ethnicity, and to demonstrate its application by developing an extended FFM model in an Indian population (FFM
Ext,Ind
).
Methods
The fundamental assumption of FFM
Jan
model development was a linear relationship between bioimpedance and body mass index. In this extension to Janmahasatian’s work, this assumption was extended to allow for potential non-linear relationships. While the original
Z
Jan
model parameters were kept fixed, a set of body composition-related parameters
Ψ
{
ψ
1
,
ψ
2
,
ψ
3
}
were incorporated, where
ψ
1
and
ψ
2
were the ethnicity factors to the intercept and the linear coefficient, respectively, and
ψ
3
a non-linear exponent. The model was then applied to data arising from a south Indian population and the
Ψ
parameters were estimated by standard non-linear regression. The data were generated from a reference model for FFM for the Indian population, which was known to provide unbiased estimates for this population.
Results
The parameter estimates (%RSE) of the final FFM
Ext,Ind
model were
ψ
1
=
0
(fixed),
ψ
2
=
0.77
(3.2%) for male patients, 0.70 (3.3%) for female patients, and
ψ
3
=
0.72
(12.4%). The final model predictions were in good agreement with the reference model predictions.
Conclusions
An FFM
Ext
model has been achieved by extending the original FFM
Jan
model assumptions to account for inter-ethnic differences in body composition. The extended model can be applied to any ethnic population by estimating a set of body composition-related parameters
Ψ
. This can be performed using bioimpedance data without the need for formal FFM measurements. |
---|---|
ISSN: | 0312-5963 1179-1926 |
DOI: | 10.1007/s40262-020-00883-1 |