An elderly patient who presented with 1 week of fever and respiratory symptoms was tested for dengue infection with an Abbott Bioline™ Dengue Duo immunochromatographic assay. Unexpectedly, the control line of the dengue non-structural protein 1 (NS1) component was absent, necessitating result invalidation. It remained absent when the test was repeated on the SD Biosensor Standard™ Q Dengue Duo, but present on the Wells Bio careUS