net change in calculates the difference between the earliest and the latest available values. For example, given the following case fragment:
01 Jun 03 20 Jun 03 30 Jun 03 15 Oct 03 02 Nov 03 HDL 2.0 2.1 2.2 2.2 1.7 LDL 4.5 4.7 3.1 Trig 3.6 3.6 LipidDrug N Y /
net change in HDL is -.3
net change in Trig < .1
net change in LDL = -1.4