Objective: It is recommended to monitoring PEFR to diagnosing OA. Gold standard method is SIC test. The aim of this study is to evaluate comparison of SIC test results in patients with OA and non-OA and to discuss PEFR monitoring and underdiagnosed.Materials and Methods: 24 patients (16 OA, 8 non-OA) who underwent SIC test were analyzed retrospectively. Results:Although number of patients exposed to LMW (wood powders [n: 5]) was higher, IgE level was found significantly higher at OA (697.39 ± 839.36 kU/ml) (p: 0.027). Average PEFR monitoring days mean was 26.53±12.90.13 patients who diagnosed with OA with SIC was evaluated PEFR monitoring results were negative [%92.86]. Minimum FEV1 value on exposure day was lower in OA (p:0.001). Conclusion:We detected underdiagnosed cases rates were higher with diagnosing OA with PEFR monitoring alone. Our study also demonstrated that LMW agents cause immunological OA, independently from agent type and duration of exposure.