Shimoda Masafumi, Saraya Takeshi, Yonetani Shota, Araki Koji, Takizawa Hajime
Department of Respiratory Medicine Department of Laboratory Medicine, Kyorin University School of Medicine, Mitaka, Tokyo, Japan.
Medicine (Baltimore). 2018 Apr;97(14):e0150. doi: 10.1097/MD.0000000000010150.
In general, physicians believe that the presence of bacterial engulfment in white blood cells (WBCs) on Gram-stained sputum is a hallmark of lower respiratory infection. However, no studies have described the significance or diagnostic accuracy of engulfment in lower respiratory tract infections.We prospectively studied sputum samples by Gram staining (Favor method) for their quality and engulfment score in WBCs obtained from patients with respiratory symptoms at inpatient and outpatient settings at Kyorin University Hospital between December 2012 and April 2015.A total of 163 patients were enrolled. The patients were classified into an infection (n = 93) or non-infection (n = 70) group based on clinical or radiological findings prior to the evaluation of sputum samples. The proportion of engulfment-positive cases was equal in the infection and non-infection groups (49.5% vs 35.7%, P = 0.11). In the infection group, the engulfment score (%) for Streptococcus pneumoniae was significantly lower (median 3%, interquartile range [IQR]: 2% to 5%, P = 0.005) than that of the non-S. pneumoniae bacteria (H. influenzae, M. catarrhalis, and methicillin-susceptible Staphylococcus aureus (MSSA))(median 22.5%, IQR: 17% to 35.5%). The engulfment score of S. pneumoniae in the WBC was low in the infection group, and no cases were recognized in the non-infection group. Using a cut-off value of 3%, the diagnostic accuracy for infection was as follows: sensitivity: 50%, specificity: 65.7%, and area under the curve (AUC): 0.579 (95% CI 0.464 to 0.694). For the non-S. pneumoniae bacteria (H. influenzae, M. catarrhalis, and MSSA), the engulfment score was significantly higher in the infection group (median 22.5%, IQR 17 to 35.5%) than in the non-infection group (median 6.0%, IQR: 3 to 13%, P = 0.011), and the diagnostic accuracy for infection was as follows: sensitivity: 75%, specificity: 85.7%, and AUC: 0.902 (95% CI 0.75 to 1.00) when the threshold for the engulfment score was defined as 18%.This study provides the first evidence that the engulfment of bacteria in WBCs is not always indicative of infection and that the engulfment score can fluctuate according to the pathogen.
一般来说，医生认为革兰氏染色痰中白细胞（WBC）内存在细菌吞噬现象是下呼吸道感染的一个标志。然而，尚无研究描述细菌吞噬现象在下呼吸道感染中的意义或诊断准确性。
我们对2012年12月至2015年4月间在杏林大学医院住院和门诊有呼吸道症状患者的痰液样本进行前瞻性革兰氏染色（Favor法）研究，以评估其质量和白细胞内的吞噬评分。
共纳入163例患者。在评估痰液样本之前，根据临床或影像学检查结果将患者分为感染组（n = 93）或非感染组（n = 70）。感染组和非感染组中吞噬阳性病例的比例相当（49.5%对35.7%，P = 0.11）。在感染组中，肺炎链球菌的吞噬评分（%）显著低于非肺炎链球菌细菌（流感嗜血杆菌、卡他莫拉菌和甲氧西林敏感金黄色葡萄球菌（MSSA））（中位数3%，四分位间距[IQR]：2%至5%，P = 0.005）（中位数22.5%，IQR：17%至35.5%）。感染组中白细胞内肺炎链球菌的吞噬评分较低，非感染组未发现此类病例。以3%为临界值，感染的诊断准确性如下：敏感性：50%，特异性：65.7%，曲线下面积（AUC）：0.579（95%CI 0.464至0.694）。对于非肺炎链球菌细菌（流感嗜血杆菌、卡他莫拉菌和MSSA），感染组的吞噬评分显著高于非感染组（中位数22.5%，IQR 17至35.5%）（中位数6.0%，IQR：3至13%，P = 0.011），当吞噬评分阈值定义为18%时，感染的诊断准确性如下：敏感性：75%，特异性：85.7%，AUC：0.902（95%CI 0.75至1.00）。
本研究首次证明白细胞内细菌的吞噬现象并不总是提示感染，且吞噬评分会因病原体不同而波动。
