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False positive Aspergillus galactomannan assay results caused by specific parenteral nutrition
Euijin Chang1, Sung-Woon Kang1, Jin-Won Huh2
1Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Republic of Korea.
Abstract:
In September 2022, the proportion of clinically false positive results with high index values for the galactomannan (GM) assay increased dramatically in our hospital and remained high until November 2022. We aimed to identify the possible causative agent that led to the dramatic increase in false positivity in GM assay. A case-control-control study was conducted, and patients admitted to two intensive care units between September and November 2022 were included. We defined each time point at which the GM assay was conducted in a patient as an episode and classified episodes into strong-positive (≥10.0 index; case), positive (control), and negative (<0.5 index; control) groups. We compared the medications administered in three groups and measured GM levels in relevant medications, including parenteral nutrition (PN). In total, 118 episodes in 33 patients were classified into three groups. There were 46 negative, 23 positive, and 49 strong-positive episodes, and there was a significant difference in the use of Winuf® PNs (P < .001) between the three groups. Forty episodes (82%) in the strong-positive group received Winuf®, compared with three (6.5%) in the negative group and one (4.3%) in the positive group (P < .001). All samples of Winuf® PNs used in the five patients whose GM results were repeatedly strong-positive were strongly positive for GM. False positivity in GM assay can be caused by the administration of specific PNs. A thorough investigation of prescribed medications should be considered when there is an abrupt increase in the proportion of strong-positive or positive GM results.
Insights
A specific parenteral nutrition product, Winuf® PN, was linked to a surge in false positive galactomannan (GM) assay results. Investigating medications is crucial when GM assay results show unexpected increases in positivity.
Area of Science:
- Clinical diagnostics
- Medical laboratory science
- Infectious disease diagnostics
Background:
- The galactomannan (GM) assay is vital for diagnosing invasive fungal infections.
- An unexplained rise in false positive GM assay results was observed in a hospital setting.
- Identifying the source of false positives is critical for accurate patient management.
Purpose of the Study:
- To investigate the cause of a dramatic increase in false positive galactomannan (GM) assay results.
- To identify specific agents or medications contributing to elevated GM assay indices.
- To determine the association between parenteral nutrition (PN) products and GM assay false positivity.
Main Methods:
- A case-control-control study design was employed.
- Patients in intensive care units were categorized by GM assay results (strong-positive, positive, negative).
- Medications, including parenteral nutrition (PN), were analyzed for their association with assay results.
Main Results:
- A significant association was found between the use of Winuf® parenteral nutrition (PN) and strong-positive GM assay results (P < .001).
- 82% of strong-positive GM episodes involved patients receiving Winuf® PN.
- All tested Winuf® PN samples from patients with repeatedly strong-positive GM results were themselves strongly positive for GM.
Conclusions:
- Specific parenteral nutrition (PN) products, such as Winuf®, can cause false positivity in galactomannan (GM) assays.
- Clinicians should consider investigating administered medications, especially PN, during unexplained increases in GM assay positivity.
- This finding highlights the importance of medication-specific interference in diagnostic testing.
