痰标本检测p53基因突变及其在肺癌早期临床诊断中的意义

目的　评价痰标本检测p53基因点突变方法及其作为肺癌早期临床诊断监测指标的真实性和可靠性。方法　用聚合酶链反应（PCR）-单链多肽性（SSCP）-银染法检测54例原发性肺癌患者和114例良性肺疾病患者痰标本中p53基因第5～8外显子的点突变，同时进行痰涂片细胞学检查。结果　p53突变在肺癌组检出率为55.56%(30/54)，非肺癌组检出率为1.75%(2/114)，P<0.001。痰标本检测p53基因突变作为肺癌临床诊断监测指标的灵敏性为55.56%，特异性为98.25%，阳性似然比为31.75。肺癌组p53阳性检出率（55.56%）与痰涂片瘤细胞阳性检出率（35.19%）比较，差异有显著性（P＜0.05），关联性有极显著意义（P＜0.01）。肺癌组p53检出率与性别、吸烟指数、病理分型、疾病分期均无明显关系，但与年龄有密切关系，高龄患者（≥60岁）检出率高（P=0.02）。结论　PCR-SSCP-银染法检测痰标本p53突变可以在可疑肺癌患者（如吸烟并慢性肺疾患者）中作为一项随访监测指标，并将有助于肺癌的早期临床诊断。

Detection of p53 gene alteration in sputum sample and its implications in early diagnosis of lung cancer

OBJECTIVES: To evaluate the value of detecting point mutation of p53 gene in sputum sample and its validity and reliability as a surveillance index in early diagnosis of lung cancer in suspicious patients. METHODS: Sputum samples were collected from 54 cases identified as lung cancer and 114 cases as pulmonary benign disease. The polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) was performed for detection of point mutation at exon 5 - 8 of p53 gene and sputum smear also used for each sample. RESULTS: A detection rate of 55.56% (30/54) in the lung cancer group is significantly higher than that of 1.75% (2/114) in the control (P < 0.001). In the lung cancer group, the sensitivity, specificity, and positive likelihood ratio of p53 alterations as a diagnostic marker of lung cancer were 55.56%, 98.25% and 31.75 respectively. Moreover, the detection rates were 35.19% (19/54) by smears and 55.56% (30/54) by PCR-SSCP-silver stain; both the difference and consistency were statistically significant (P < 0.01 and P < 0.05 respectively). Statistic analysis did not show any significant relation between p53 alteration and clinical parameters such as gender, smoking habits, histotypes and stages, but the detection rate of p53 alteration in older patients (>or=60 years old) was significantly higher than that in younger (P = 0.02). One case with p53 alteration at exon 5 in the control group was confirmed to be squamous carcinoma after 4 years of follow-up. CONCLUSION: Detection of p53 gene alteration in sputum sample by PCR-SSCP-silver stain can be used as a follow-up surveillance index for early diagnosis of lung cancer in suspicious patients.