Summarizing Laboratory Data with Different Reference Ranges in Multi-Center Clinical Trials

In this paper, we propose a procedure to summarize the lab data obtained from laboratories which have different reference ranges in a multi-center clinical trial. The procedure calls for first standardizing lab values relative to their respective reference ranges. Unit-free intermediate summary statistics are obtained based on the standardized values. The procedure then restores the unit by using the reference ranges from the center with the highest patient enrollment. Two methods to standardize the lab values and the relationship between them are discussed. Two examples are given to illustrate the proposed procedure and to demonstrate why procedures such as the one proposed in this paper are necessary.