A further comment on measurement of thyrotropin.

procedure and cannot be attributed to spectrophotometric insensitivity. (The major drawback of the Isomune-CK procedure is that it requires a sensitive spectrophotometer for the CK measurements.) Good precision is probably not mandatory for CK-MB quantitation when monitoring patients who have had acute myocardial infarcts, but we believe that it is essential when following patients who have undergone open-heart surgery. At our hospital, open-heart surgery patients are discharged from the intensive-care unit as soon as their CK-MB values drop below 15 UIL. In our hands, the Isomune-CK procedure provides adequate precision to make this decision, whereas the TANDEM procedure does not.