This article is for lab techs, not programmers. You won't need to know BASIC, Cobol or Excel.^® You'll need to know what a calculation should do in your information system and what it should not. I'll use glomerular filtration rate (GFR) in CPSI as an example, but the concepts apply to any LIS.

Estimating GFR
GFR assesses the filtering capacity of the kidneys, traditionally estimated by the urine creatinine clearance test. But 24-hour urine collections are inconvenient and not always reliable. The National Kidney Disease Education Program (NKDEP) suggests that laboratories report an estimated GFR using the modification of diet in renal disease (MDRD) prediction equation:¹

GFR (mL/min/1.73 m²) = 186 x (P_cr )^-1.154 x (Age)^-.203 x (.742 if female) x (1.210 if African American)

The NKDEP has an online calculator, but you'll want to add it to each report. It should work in the background and be free of errors.² Before you call your LIS vendor, there are a few things to consider.

The GFR calculation is complicated by conditions that are represented by the "if" statements. If the patient is female, then multiply by .742. Such "branching logic" changes a program's course.

Computers use branching to reuse code and save space. It's really shorthand for more than one calculation, and it can make a problem appear more complicated than it is.

Ask Yourself .
With GFR, you first need to know the variables. They are creatinine, sex, race and age.

Does your LIS "know" this information?

The answer isn't always obvious. CPSI can only access numerical results that appear in the same report above the calculation. Sex, race and age aren't variables that can be used, even though CPSI "knows" what they are.

This is important information to have before you begin. It suggests that to program GFR, some of the information will have to be entered manually, inviting human error and reducing efficiency.

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