From the Guidelines
The incidence of false positives in fit tests is not explicitly stated in the provided evidence, but it can be inferred that false positives may occur due to various factors such as face-seal leakage or filter leakage, which cannot be distinguished by fit tests. When interpreting fit test results, it is essential to consider the limitations of the tests, as they can only detect leakage at the time of testing 1. Some key points to consider when evaluating fit test results include:
- The test can detect only the leakage that occurs at the time of the fit testing
- The tests cannot distinguish face-seal leakage from filter leakage
- The healthcare worker (HCW) may need to be fit tested with several devices to determine which device offers the best fit Given the potential for false positives due to these limitations, it is crucial to carefully evaluate fit test results and consider additional factors that may influence the accuracy of the test. In real-life clinical practice, this means that healthcare providers should be cautious when interpreting fit test results and consider the potential for false positives when making decisions about respiratory protective devices 1.
From the Research
Incidence of False Positives in Fit Tests
- The incidence of false positives in fit tests is not directly addressed in most of the provided studies, which focus on the comparison of qualitative and quantitative fit-testing results, the performance of different respirator models, and the risk factors for false-positive and false-negative results in colorectal cancer screening 2, 3, 4, 5, 6.
- However, a study on qualitative fit test outcomes for N95 filtering facepiece respirators in health care workers found an overall failure rate of 15.2%, but this does not specifically address false positives 6.
- Another study compared qualitative and quantitative fit-testing results for three commonly used respirators in the healthcare sector and found a disagreement in outcomes between the two fit-test methods of approximately 12%, which may include both false positives and false negatives 4.
- A study on participant-related risk factors for false-positive and false-negative fecal immunochemical tests in colorectal cancer screening found that male sex was associated with a significantly lower risk of false-positivity, while participants using non-steroidal anti-inflammatory drugs had a higher risk, but this is not directly related to fit tests 5.
Risk Factors for False Positives
- Male sex was associated with a significantly lower risk of false-positivity in a study on participant-related risk factors for false-positive and false-negative fecal immunochemical tests in colorectal cancer screening 5.
- Participants using non-steroidal anti-inflammatory drugs had a higher risk of false-positivity in the same study 5.
- However, these risk factors are not directly related to fit tests, and more research is needed to identify risk factors for false positives in fit tests.
Comparison of Qualitative and Quantitative Fit-Testing Results
- A study compared qualitative and quantitative fit-testing results for three commonly used respirators in the healthcare sector and found a disagreement in outcomes between the two fit-test methods of approximately 12% 4.
- Another study evaluated three qualitative respirator fit tests and found that the probability of passing or failing a qualitative test with an inadequately fitting respirator can be estimated, but the uncertainty associated with each estimate is large due to the small number of study subjects with poorly fitting respirators 3.