262. Assessment of Serum Galactomannan Test Results of Pediatric Patients with Hematologic Malignancies According to Different Threshold Levels and Consecutive Positivity in Terms of Invasive Aspergillosis Diagnosis: Cross-Sectional Research in a Tertiary Care Hospital

Abstract Background The aim of this study was to evaluate the diagnostic utility of serum galactomannan (GM) test by investigating the impact of positivity according to different threshold levels and consecutiveness in terms of invasive aspergillosis (IA) in pediatric hematology-oncology patients. Methods Positive GM test results between January 2015 and August 2017 were reviewed, retrospectively. The children with hematological malignancies and GM positivity were included in the study and grouped according to the presence of IA. Impact of single and consecutive (3-day interval) GM positivity on IA diagnosis were evaluated according to different galactomannan index (GMI) threshold values of >0.5, >0.7, >1.0, and >1.5. Results There were 104 positive GM results from 70 patients. Forty-one patients (58.6%) had no clinical evidence of IA and categorized as the non-IA group. Invasive aspergillosis diagnosis was identified in 29 (41.4%) of the patients; 2 of them were proven and 27 were probable. Demographic characteristics and clinical findings of the patients were reviewed in Tables 1 and 2. According to different cutoff GMI values, the number of positive results was 104 for >0.5, 76 for >0.7, 57 for >1.0 and 32 for >1.5. The PPVs were low at a single GMI of >0.5 (39.4%) and reached to 50.0% with single GMI of >1.0. There was not a statistically significant difference between IA and non-IA groups in terms of different thresholds of a single GM positivity (P > 0.05) (Table 3). The number of two consecutive positive results was 34 for GMI of >0.5, 20 for GMI of >0.7, 13 for GMI of >1.0 and 4 for GMI of >1.5. In the IA group, GM positivity of consecutive results was significantly higher than non-IA group (P < 0.05). The PPVs of two consecutive positive results for GMI >0.5, GMI >0.7, GMI >1.0, and GMI >1.5 were 58.8%, 65.0%, 84.6%, and 100.0%, respectively. The effect of the GMI increase between two consecutive GM results on IA diagnosis (GM2-GM1 >0.5) was also evaluated and the PPV was found 53.8% without a statistical significance between two groups (Table 4). Conclusion When evaluated with consecutive GM positivity, the GM assay would have higher PPVs independently from the GMI cutoff value chosen. Since it may be more effective on IA diagnosis, consecutive sampling should be performed in pediatric patients at high risk. Disclosures All authors: No reported disclosures.