To analyse the significance of methylation test of Ras association family 1 isoform A (RASSF1A) and short stature homeobox 2 (SHOX2) in bronchoalveolar lavage fluid(BALF) combined with radial ultrasonic features in the differential diagnosis between malignant and benign pulmonary nodules.

Ninety patients with pulmonary nodules admitted to our hospital from September 2022 to March 2024 were selected, 54 cases of malignant pulmonary nodules diagnosed by histopathology were in the observation group, and 36 cases of benign pulmonary nodules were in the control group, and BALF was collected for cytological examination and methylation detection of the RASSF1A and SHOX2 genes to compare the methylation positivity rate of the two groups and analyse the sensitivity and specificity of pulmonary nodules. Logistic regression analysis was used to screen some clinical characteristics, radial ultrasonic features and methylation indexes as predictors to construct a prediction model of pulmonary nodules.

In the observation group, 22 cases (40.74%) of RASSF1A positivity were higher than 1 case (2.78%) in the control group(P<0.01); 25 cases (46.30%) of SHOX2 positivity were higher than 2 cases (5.56%) in the control group(P<0.01); 14 cases (25.93%) of both RASSF1A and SHOX2 positivity were higher than 1 case(2.78%) in the control group(P<0.05); 33 cases (61.11%) of RASSF1A or SHOX2 positivity were higher than 2 cases (5.56%) in the control group(P<0.01; The sensitivity for diagnosing malignant lung nodules was 61.11% and the specificity was 94.44% for the positivity of RASSF1A or SHOX2. 33 cases (61.11%) of RASSF1A or SHOX2 positivity were significantly higher than 17 cases(31.48%) of BALF cytology positivity(P<0.05); Radial ultrasound characteristics of the observation group in the ratio of the continuous margins of 81.40%, the ratio of the uneven internal echo of 83.72% and the ratio of hypoechogenic shadows of 72.09% were higher than that of the control group of 40.00%, 40.00%, 45.71% (P<0.05); Multifactorial logistic regression analysis showed that two-gene methylation, continuous margins and uneven internal echo were the risk factors for predicting malignant lung nodules, and the area under the curve (AUC) of the working characteristics of the subjects was 0.886.

RASSF1A combined with SHOX2 methylation detection of BALF is valuable for the diagnosis of malignant lung nodules, and RASSF1A and SHOX2 methylation combined with radial ultrasound features are clinically relevant for the differential diagnosis of the property of lung nodules.