A panel comes back with one number missing an explanation

A nonfasting serum specimen arrives at 0800 with a mild turbid appearance. Forty-two minutes later the analyzer releases a lipid panel: total cholesterol (TC) 210 mg/dL, HDL-cholesterol (HDL-C) 42 mg/dL, triglycerides (TG) 220 mg/dL, LDL-cholesterol (LDL-C) 124 mg/dL, and non-HDL-C 168 mg/dL. Only three of those five numbers came off the analyzer as a direct measurement. The other two, LDL-C and non-HDL-C, were calculated from the first three by the laboratory information system before the report ever reached the clinician.

That distinction matters at the bench. A measured result carries the accuracy and imprecision of the assay that produced it. A calculated result carries that same uncertainty plus whatever the calculation equation assumes about the specimen, and some of those assumptions break down at exactly the triglyceride concentrations a laboratory sees every shift. A specimen with a visibly turbid, lipemic appearance is one of the clues that an assumption might be under strain before a single number is even reviewed.

Before releasing or interpreting any lipid result, know whether it came off the analyzer or came out of an equation, because that changes what a high or low number can mean.