Comparison of diagnostic efficacy of galactomannan lateral flow assay vs enzyme immunoassay: importance of storage conditions

Abstract

Introduction: Galactomannan antigen is a valuable biomarker for diagnosing invasive aspergillosis. Traditional methods, such as enzyme immunoassays (EIA), require batch sampling, whereas lateral flow assays (LFA) provide a simpler and faster diagnostic process. This study aimed to compare the diagnostic efficacy of both testing methods.

Methodology: This prospective case-control study involved 192 serum samples categorized according to the European Organization for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG criteria). LFA were conducted following the manufacturer’s instructions, utilizing a cube reader. Receiver operating characteristic (ROC) analysis was performed to determine the optimal LFA threshold, and concordance analysis was conducted for both assays.

Results: The indicated sensitivity and specificity of LFA at the recommended galactomannan index threshold (GMI ≥ 0.5) were 15.3% (9/59) and 99% (132/133), respectively. Post-ROC analysis at a threshold of 0.4 revealed an area under the curve (AUC) of 0.685, with sensitivity, specificity, positive predictive value, and negative predictive value at 18%, 99%, 91%, and 73%, respectively. Qualitative agreement between the tests, assessed using the Kappa statistic, indicated a very low degree of agreement (κ = 0.18). In contrast, quantitative agreement, evaluated through Kendall’s W-test, demonstrated a very high degree of agreement (W = 0.84).

Conclusions: Despite previous literature suggesting the efficacy of LFA, our study found it unsuitable for screening due to its low sensitivity. We recommend exercising caution regarding the manufacturer's storage recommendations until further studies on sample storage conditions are conducted.