Optimization and staining characteristic of immunohistochemical methods in detecting isocitrate dehydrogenase-1 mutations in human gliomas

Objective To compare the advantages and disadvantages of different immunohistochemical methods in detecting isocitrate dehydrogenase-1(IDH1)mutations in gliomas, and to optimize the processes these detection. Methods One hundred and thirty-eighty glioma specimens, collected and conformed by pathology in our hospital from January 2013 to December 2013, were used in our study, including 18 of WHO grade I, 49 of WHO grade II, 24 of WHO grade III and 47 of WHO grade IV. Manual immunohistochemical method and automatic immunohistochemical instrument were used to detect the IDH1 mutation. PCR-high resolution melting curve analysis(PCR-HRM)was used to verify the above results. Results There were 65.9% positive specimens those had IDH1 positive tumor cells higher than 75%, and 70.7% positive specimens those were strong staining. Manual immunohistochemical method enjoyed advantages as clean background, clearness and easy reading, and no interpretation difficulty or false-positive result were noted with this method; while automatic immunohistochemical instrument enjoyed dark background, which led to interpretation difficulty or false-positive result; the results of IDH1 staining had significant differences between and automatic immunohistochemical instrument(χ2= 22.042, P=0.000). The positive detection rate of automatic immunohistochemical instrument was significantly higher than that of manual immunohistochemical method, and the results of IDH1 detection had no significant difference between manual immunohistochemical method and PCR-HRM(χ2=0.800, P=0.371). Conclusions The results of IDH1 detection by manual immunohistochemical method are more accurate than that of immunohistochemical instrument. IDH1 gene mutation only has a relationship with the number of positive tumor cells, and not the staining intensity. The specimen can be considered to IDH1 gene mutation when the positive cells are more than 5%. Key words: Glioma; Isocitrate dehydrogenase-1; Immunohistochemistry