False positive results of galactomannan ELISA assay in haemato-oncology patients: a single centre experience

Multiple myeloma as a major cause of false-positive galactomannan tests in adult patients with cancer

OBJECTIVES

The galactomannan (GM) test is a useful method for early diagnosis of invasive aspergillosis. Recently, multiple myeloma has newly been suggested to be related to false-positive results of GM. We performed a case-control study to validate this finding.

METHODS

Electronic medical records were reviewed for patients admitted March through June 2014. Patients with false-positive GM results were selected as cases and those with negatives as controls. To verify the results of the four-month analysis, additional analysis was performed in multiple myeloma patients over a three-year period.

RESULTS

There were 30 false-positive and 316 negative cases during the four-month period. Among the factors evaluated, multiple myeloma was the only significant factor in the adjusted analysis (OR = 3.59, CI 1.28-10.04). In the three-year analysis of 145 multiple myeloma patients, 25.5% showed false-positive results, which was 3 times higher than overall. GM false-positivity was not related to serum monoclonal protein level or type of immunoglobulin. GM optical density indexes (ODIs) in all false positives were lower than 3.0.

CONCLUSIONS

Multiple myeloma was a major cause of GM false-positivity in adult cancer patients. GM was false-positive in 25.5% of multiple myeloma patients with GM ODIs lower than 3.0.

Generic piperacillin/tazobactam is not associated with galactomannan false-positivity in adult patients with cancer: a case-control study

Recent products of piperacillin/tazobactam (PTZ) from the original manufacturer, previously considered a major cause of galactomannan (GM) false-positivity, are reported not to be related to it. However, data regarding generic PTZ are limited and controversial. To evaluate the effect of generic PTZ on GM false-positivity in Korea, we performed a case-control study in adult patients with cancer. A case-control study was designed. Electronic medical records of cancer patients who were admitted and tested for serum GM between March and June 2014 at a tertiary care university hospital were reviewed. During the study period, a single generic PTZ (C manufacturer, Korea) was used. Patients who received PTZ within 24 h prior to serum GM testing were enrolled. Age- and GM test date-matched non-PTZ patients were selected as controls. A total of 110 patients received PTZ within 24 h prior to serum GM testing during the study period. The GM optical density index (ODI) of the PTZ group did not vary significantly from that of the control group (p = 0.251). The percentage of false-positive patients in the PTZ group was also similar to that of the control group (p = 0.538). There was no statistical relationship between GM ODI titer and time interval from PTZ administration (p = 0.095) or cumulative PTZ dose (p = 0.416). In a case-control study that evaluated 220 patients, a generic PTZ in Korea was not related to GM false-positivity.

PCR-based diagnosis of human fungal infections

PCR is a very appealing technology for the detection of human pathogens, but the detection of fungal pathogens is particularly challenging. Fungi have cell walls that impede the efficient lysis of organisms and liberation of DNA, which can lead to false-negative PCR results. Conversely, some human pathogens are also ubiquitous environmental saprophytes that can contaminate PCR reagents and cause false-positive results. We examine the quality of PCR-based studies for fungal diagnostics using 42 variables within the Minimum Information for Publication of Quantitative Real-Time PCR Experiments guidelines. This review focuses on taxon-directed PCR assays for the diagnosis of invasive aspergillosis, candidiasis and Pneumocystis pneumonia. Finally, we evaluate broad-range fungal PCR assays capable of detecting a wide spectrum of human pathogens.