Curve fitting of labeled platelets: gamma model expanded for severe pathology.

To obtain an adequate curve fitting of labeled platelets also in case of severe pathology the multiple hit model of Murphy & Francis can be used, however, with addition of fractions of n (argument of the gamma function) and expansion of the domain of n towards zero and negative values. The 'hazard rate function' provides the instantaneous death rate for a platelet that has survived up to a given time. Applied to the multiple hit function, three kinds of hazard rate will be found: for n > 1 the death rate increases with age (absent or moderate pathology); for n = 1 the death rate is independent of age (death at random); for n < 1 the death rate decreases with age (probably severe pathology).