RT Journal Article SR Electronic T1 Aerosolised fluorescein can quantify FFP mask faceseal leakage: a cost-effective adaptation to the existing point of care fit test JF Clinical Medicine JO Clin Med FD Royal College of Physicians SP e263 OP e268 DO 10.7861/clinmed.2020-0982 VO 21 IS 3 A1 Sameer Zaman A1 Henry Seligman A1 Freya Hepworth Lloyd A1 Keval T Patel A1 Digby Chappell A1 Danny O'Hare A1 Graham D Cole A1 Darrel P Francis A1 Ricardo Petraco A1 Nick WF Linton YR 2021 UL http://www.rcpjournals.org/content/21/3/e263.abstract AB Background A qualitative fit test using bitter-tasting aerosols is the commonest way to determine filtering face-piece (FFP) mask leakage. This taste test is subjective and biased by placebo. We propose a cheap, quantitative modification of the taste test by measuring the amount of fluorescein stained filter paper behind the mask using image analysis.Methods A bitter-tasting fluorescein solution was aerosolised during mask fit tests, with filter paper placed on masks' inner surfaces. Participants reported whether they could taste bitterness to determine taste test ‘pass’ or ‘fail’ results. Filter paper photographs were digitally analysed to quantify total fluorescence (TF).Results Fifty-six healthcare professionals were fit tested; 32 (57%) ‘passed’ the taste test. TF between the taste test ‘pass’ and ‘fail’ groups was significantly different (p<0.001). A cut-off (TF = 5.0 × 106 units) was determined at precision (78%) and recall (84%), resulting in 5/56 participants (9%) reclassified from ‘pass’ to ‘fail’ by the fluorescein test. Seven out of 56 (12%) reclassified from ‘fail’ to ‘pass’.Conclusion Fluorescein is detectable and sensitive at identifying FFP mask leaks. These low-cost adaptations can enhance exiting fit testing to determine ‘pass’ and ‘fail’ groups, protecting those who ‘passed’ the taste test but have high fluorescein leak, and reassuring those who ‘failed’ the taste test despite having little fluorescein leak.