The urinary antigen test (UAT) is a rapid diagnostic method for pneumococcal pneumonia, but the high false-negative rate of 30% may affect its reliability. To maximize the utility of UAT, it is necessary to investigate the patient factors affecting UAT results. However, there is no report elucidating the association between its utility and pre-existing lung abnormalities. We retrospectively reviewed 388 patients with pneumococcal pneumonia confirmed by blood and/or sputum culture tests. Finally, 94 of 388 patients who had the results of UAT and computed tomography scans were enrolled to evaluate the association between the utility of UAT and patient factors including pulmonary emphysema and fibrosis. The overall positive rate of UAT was 69.1%. The positive rates of UAT in the patients with emphysema were significantly lower than those in individuals without emphysema (33.3% and 77.6%, p < 0.001). Univariate logistic regression analysis showed that the presence of emphysema was associated with a low positive rate (odds ratio 6.944, 95% confidence interval 2.268–21.231). Multivariate logistic analysis showed that the presence of emphysema and lower levels of serum blood urea nitrogen (BUN) were significantly and independently associated with a low positive rate. The combination of emphysema and BUN can potentially stratify the positive rate of UAT in patients with pneumococcal pneumonia. Patients with pneumococcal pneumonia and emphysema have a lower positive rate of UAT. Additionally, the combination of emphysema and serum BUN value may be useful to evaluate the reliability of the negative results of pneumococcal UAT.

尿抗原检测（UAT）是肺炎球菌肺炎的快速诊断方法，但30%的高假阴性率可能影响其可靠性。为了最大限度地发挥 UAT 的效用，有必要调查影响 UAT 结果的患者因素。然而，没有报告阐明其效用与预先存在的肺异常之间的关联。我们回顾性地审查了 388 名经血液和/或痰培养试验确诊的肺炎球菌肺炎患者。最后，388 名获得 UAT 和计算机断层扫描结果的患者中的 94 名被纳入评估 UAT 的效用与患者因素（包括肺气肿和纤维化）之间的关联。UAT总体阳性率为69.1%。p  < 0.001)。单变量逻辑回归分析显示肺气肿的存在与低阳性率相关（优势比 6.944，95% 置信区间 2.268-21.231）。多变量逻辑分析表明，肺气肿的存在和血清尿素氮 (BUN) 水平较低与低阳性率显着且独立相关。肺气肿和 BUN 的组合可能对肺炎球菌肺炎患者的 UAT 阳性率进行分层。肺炎球菌肺炎和肺气肿患者UAT阳性率较低。此外，肺气肿和血清 BUN 值的组合可能有助于评估肺炎球菌 UAT 阴性结果的可靠性。