Determine the relationship between fraction exhaled nitric oxide (FeNO) and mannitol challenge test in the diagnosis of suspected asthma patients

Method: A cross-sectional study from February 2019 to November 2019. Calculated sample size: 126. A descriptive analysis was conducted. A student T study was conducted to compare the mean FeNO (ppb) levels between the positive and negative mannitol test groups. Pearson9s correlation study between FeNO (ppb) and PD15 (mg) levels were performed. Results: Patients finally analyzed were 111 patients. The descriptive study is shown in Table 1. Differences between FENO levels and mannitol results (positive/negative) were found. The mean FENO of mannitol-positive patients was 58.8 (SD 56) ppb and the mannitol test was negative 18.7 (SD 11.1) ppb (p 0.000). A negative relationship was found between FeNO levels and PD15 (r -0.45 ; p 0.000). Only one of the patients with FeNO levels above 50 ppb had a positive mannitol test, the rest of the patients with FeNO above 50 ppb had a positive mannitol test. Conclusions: The results found in the analyzed sample show that a result higher than 50 ppb FeNO with a compatible asthma clinic could avoid the performance of a non-specific provocation test with mannitol for the diagnosis of asthma. However, a FeNO result below 50 ppb does not exclude a positive mannitol test and therefore the diagnosis of asthma.