False-Positive Platelia Aspergillus (PA) Test in Patients (pts) Receiving Piperacillin-Tazobactam (P/T)

C. VISCOLI, M. MACHETTI, P. CAPPELLANO, B. BUCCI, P. BRUZZI, A. BACIGALUPO

Author address: 

Natl. Inst. Cancer, Univ. of, Genova, Italy, Fed. Univ., Sao Paulo, Brazil, San Martino Hosp., Genova, Italy.

Abstract: 

Background:The PA test, recently approved by the FDA, detects aspergillus galactomannan (GM) in blood and may be an indicator of invasive aspergillosis (IA). In our center the test is employed in BMT patients since Jan.1999. In terms of blood samples, the median positivity rate per month increased from 8.6% (range 0-18.5%) in the period Jan. 99-Jan. 03 to 23.7% (19.6-44.5%) in the period Feb-May 03. Overall, in this period 21 of 59 patients (35.6%) or 150 of 538 samples (27.9%) tested positive at the PA. Methods: Technical methods, clinical histories of positive pts and supportive care measures were reviewed, in order to understand the reason for this increase. Results: No change in blood samples processing was done. Technically, the test was working as expected. An IA outbreak was excluded. Indeed, of the 21 pts who tested positive in the period Jan-May 03, 4 had probable and 17 had possible IA. Among the 4 pts with probable IA, only 1 had a truly probable disease ( aspergillus in sputum with cavitated lung lesions), while the others would not have been classified as probable IA, without the PA test. The 17 pts with possible IA had virtually no symptoms and were classified as possible IA only because of the positive PA test. In terms of supportive care procedures, the only change was the use of P/T instead of ceftazidime as empirical therapy of suspected infection. A quick investigation showed that the proportion of positivity (at least 2 positive results) was 73.9% (17 of 23) among pts receiving P/T vs. 11.1% (4 of 36) among those not receiving P/T(p
2003

abstract No: 

M-2062b

Full conference title: 

43rd Interscience Conference on Antimicrobial Agents
    • ICAAC 43rd