carbon clearance test is one of the easy test to perform for identification of effect of drugs on phagocytosis (indirect measurement to understand the effect on reticulo endothelial system). If we see the (origin) article in which the formula was mentioned, they have included the consideration liver and spleen weight along with clearance rate in the formula to calculate phagocyitc index.

But in most of the papers, people are not considering liver and spleen weight and concluding clearance rate as Phagocyitc index.

How far it is justifiable to do so?

In my experience results are completely different in the two ways.

Is there any justification in modifying original formula?