Happy Holidays!
For a serious diagnosis like pheo, repeat testing of pheo markers is generally a good idea. Pheo test results from the same patient even within a few days or weeks can be quite different at times. Patients having acute illness, anxiety attack, or any emotional or physical stress would have higher pheo marker levels than when they are healthy and restful. The position (sitting or lying) of patients getting blood draw matters. Random variations are always possible. Laboratory errors do happen as well. If the two test results are concordant (which fortunately are more common), we can confidently say whether the patient has normal or abnormal pheo marker levels. If, however, the two test results are discordant (one abnormal and one normal, or one very high and one only slightly high), what shall we do?
There are several factors to consider. First, we need to see the quantitative differences between the two results. If one result is in the high normal range and the other slightly abnormal, they are essentially similar and concordant results. Second, we need to delve into the details on the patient’s mental and physical condition when the tests are done. If the patient is seriously ill when one test is taken, the result is likely higher and does not necessarily suggest pheo. Third, we need to ask ourselves the likelihood of this patient’s having pheo is high or not, based on the grounds why we test for pheo in the first place. Of course the more suspicion we have, the more likely the abnormal result is true. Fourth, past research has shown that if there are no laboratory errors, a single normal test result rules out pheo in most patients. Thus a negative pheo test result should be given more weight in general. Last, when we are really not sure, imaging is needed to give us more information.
Dr. Pheo
