Quantitative fit-test concordance of a pair of similar-fit 3M Aura respirator models, 3M 9320A+ and 3M 1870+: A randomized crossover study

Abstract

Objective: Some manufacturers provide information on similar-fit model pairings of filtering facepiece respirators (FFRs), suggesting that fit-test outcome of one model helps predict the other. This guidance may be useful during crisis capacity when FFR supplies and/or fit tests are constrained. The purpose of this study was to compare quantitative fit-test (QNFT) results and concordance between a pair of similar-fit 3M Aura FFRs: the 3M 9320A+ and 3M 1870+. Methods: All participants completed online training and a QNFT with both respirators. The order of the respirator being examined first was randomly allocated. The outcomes included QNFT pass rate, concordance between the 2 models, overall and individual fit factors, and percentage of male and female participants who passed or failed the QNFT. Results: We recruited 1,000 participants (668 females and 332 males). The QNFT pass rate, overall fit factors, and individual fit factors were significantly higher for the 3M 9320A+ than the 3M 1870+ FFR. The concordance between the models was “fair” (κ coefficient, 0.38). Male participants who passed a QNFT with either of the FFRs had 96% chance of passing the QNFT for the alternate model. Female participants who passed the 3M 1870+ had 97% chance of passing the QNFT for the 3M 9320A+ model. However, ∼1 in 12 females who passed the QNFT for the 3M 9320A+ failed the QNFT for the 3M 1870+ FFR. Conclusions: Similar-fit paired FFR models may provide a consequentially different level of respiratory protection, especially for women. Our findings are important for FFR stockpiling and fit-testing strategies, especially during crisis capacity.

A systematic review of passing fit testing of the masks and respirators used during the COVID-19 pandemic: Part 1-quantitative fit test procedures

“…Thirteen studies reported that there were significant differences in passing fit test rates of masks or respirators [ 39 – 41 , 65 , 69 , 77 , 94 , 108 , 111 , 127 – 131 ]. In the study by Martelly et al, the significant level was not reported; however, due to the considerable difference between the two studied respirators, it could be considered as a statistically significant difference in terms of FF (7.0 vs. 143) [ 129 ].…”

“…Eight studies looked at the effect of gender on fitting ability [ 32 , 37 , 66 , 78 , 89 , 107 , 111 , 114 , 117 ], with four of these highlighting that males had a higher pass rate than females [ 66 , 89 , 111 , 117 ]. Christopher et al highlighted the reasons for failing the fit test for females, including facial asymmetry (8%), small bones (77%), and none reported (15%), and the reasons for males, including facial hair (91%), large bones (3%), and small bones (6%) [ 89 ].…”

“…Christopher et al highlighted the reasons for failing the fit test for females, including facial asymmetry (8%), small bones (77%), and none reported (15%), and the reasons for males, including facial hair (91%), large bones (3%), and small bones (6%) [ 89 ]. In the study by Williams et al, although males had a higher passing rate than females; however, females were fitted with the 3M 9320A more often than males (7.3% vs. 1.5%, p< 0.001) [ 111 ]. In contrast, some other studies reported that females had a higher pass rate than males [ 78 , 107 , 114 ].…”

“…participants [101,102], two studies: Japan University of Occupational and Environmental Health [103,104], one study: employees of the National Institute for Occupational Health (NIOH) [105], and one study: American Society of Safety Professionals (ASSP) [54]. Notably, the HCW subjects' occupations or professional groups were not mentioned in nineteen studies [32,33,42,51,53,58,88,[106][107][108][109][110][111][112][113][114][115][116][117]. The subjects' occupations in the remaining 69 studies were not exactly determined.…”