Obesity is almost invariably present in Cushing, but is of little diagnostic value because of its high incidence in the population as a whole , particularly in women between the age of 20 and 50 years who are the most likely to be suffering from Cushings Syndrome. Clinical acumen, however, is insufficient to establish the diagnosis, and confirmation depends on showing that cortisol production is in excess of normal. Because obesity is increasing at an alarming rate throughout the world (estimated >300 million obese people world-wide), we noted a concordant increase in number of patients being sent for Cushing screening tests. In our practice the 24 hours urine collection for free cortisol UFC is our first line screening test; overnight dexamethasone suppression test ODST being second line. Our lab has been subjected to increasing number of UFC test. UFC is cumbersome test not only for the patient but also the lab staff. We felt that the ODST could be as sensitive as the UFC, but less hassling and easier to perform; not to mention more cost effective. Hence came the idea of auditing our practice. We looked at clinical notes of 62 patients who underwent the Cushing screening tests. We studied the notes with regards to which screening tests was performed (UFC, ODST or both) and what is the final outcome (true / false positive or true / false negative). We excluded 12 patients as they performed the test UFC for the purpose of cortisol replacement monitoring of Addisons disease. 66% were female and 33% male. 40% has UFC alone and 60% both. 66% requested by Endocrinologist, 26% by Hospital General Physician and 8% by GP. For UFC 20% was true positive, 62% false positive, 12% true negative and 0% false negative. Out of the false positives 6 cases due to alcohol excess, 4 depression, 3 on inhaled steroid and 1 on OCP. For the ODST 22.6% true positive, 12.9% false positive, 64.5% true negative and 0% false negative. Out of the false positive 1 case due to alcohol excess and 1 depression. In conclusion the ODST can be used reliably as first line screening test. It is easier to do for both patient and lab. Furthermore It is more cost effective. However if Cushing Syndrome is highly suspected clinically or ODST is positive we proceed for UFC test. We are not omitting the UFC test but we making it as second line.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.