735 - Trends and Cost Analysis of Aspergillus Galactomannan testing at a Tertiary Medical Center.

Background: Aspergillus is a fungus spread by inhalation of spores that can lead to invasive (IA), chronic, or allergic aspergillosis. Risk factors for IA include neutropenia, hematological malignancy, allogenic stem cell (HSCT) or solid organ transplant, severe immunodeficiency, or prolonged steroid use.   An alternative to invasive tissue sampling, the serum Galactomannan (AGM) test detects a polysaccharide cell wall component of Aspergillus and can be used to determine a probable diagnosis of IA.  Accuracy of AGM is related to disease burden and thus has the highest sensitivity and specificity in patients with hematologic malignancy or Hematopoietic stem cell transplantation (HSCT) at 70-82% and 86-92%, respectively.  Studies have shown sensitivity to decline in other populations, with solid organ transplants as low as 20%.

Methods: We performed a retrospective study of all patients who received the AGM test at UMMC from January 3, 2013 to December 31, 2019. Patient Cohort Explorer was used to obtain de-identified patient data from EPIC. We obtained the number of encounters and patients on whom the AGM test was performed along with other variables. Billing offices provided the self-pay cost per AGM test.

Results: A total of 6,404 AGM tests were performed on 2,126 patients during 4,315 encounters in the study period. With a total of 499, 574, 984, 1140, 851, 1175 and 1181 tests done respectively from 2013 to 2019, a increasing trend was noted. The patients ages ranged from 1 to 89 with a median age of 52 years. A total of 3,055 tests were ordered in females, and 3,349 were ordered in males.  
At a cut off value (optical density index) of > 0.5, 183 AGM tests resulted positive in 108 patients and at a cut of > 1.0, 113 tests are positive in 70 patients. The rate of a positive AGM tests at > 0.5 was at 2.85% and at > 1.0 was at 1.76% over the study period. With the self-pay cost of each test at $134.54 in 2019 USD, the total cost of 6,404 tests was $861,594.16.

Conclusion: To our knowledge this data set constitutes the largest sample size of AGM testing. From our data, it seems that the rate of ordering this test has increased yearly. Relatively low percentage of these tests are positive, suggesting that it is most likely a large amount of these tests could have been ordered inappropriately or in the wrong clinical context.