METHODS:Specimens of infected corneal tissue were collected from 74 cases(75 eyes), and then they were divided into an AK group and a non-Acanthamoeba keratitis(NAK)group based on the results of corneal scraping, culture and histopathological diagnosis. The tissues of consecutive sections were stained with HE staining, PAS staining and fluorescence respectively, and the sensitivity and specificity of the three staining methods for the diagnosis of AK were analyzed. Area under the curve(AUC)was calculated using the receiver operating characteristic(ROC)curve. Further analysis was performed to count the number of Acanthamoeba pathogens found by the three staining methods under the same magnification field of view at the same site, and to clarify the diagnostic value of fluorescent staining technique for AK.

RESULTS: The sensitivity of HE staining was 69%(27/39)with a specificity of 92%; the sensitivity of PAS staining was 62%(24/39)with a specificity of 97%, and the sensitivity of fluorescent staining was 95%(37/39)with a specificity of 97%. There were differences in the sensitivity of the three staining methods for the diagnosis of AK(χ2=19.857, P<0.001), and pairwise comparison revealed that the differences between HE staining and fluorescent staining, PAS staining and fluorescent staining for the diagnosis of AK were statistically significant(P=0.003,<0.001), while the difference in sensitivity between HE staining and PAS staining for the diagnosis of AK was not statistically significant(P=0.978). The maximum AUC was 0.960 for fluorescence staining, followed by 0.804 for HE staining and 0.794 for PAS staining, respectively. The median number of amoeba cysts detected by HE staining, PAS staining and fluorescent staining at the same site under the same magnification field of view was 4(0, 11), 2(0, 9)and 12(3, 33), respectively(χ2=56.561, P<0.001). Pairwise comparison revealed that the differences in the number of amoeba cysts found by HE staining and fluorescence staining, PAS staining and fluorescence staining were statistically significant(P<0.001), while the difference in the number of amoeba cysts found by HE staining and PAS staining was not statistically significant(P=0.210). Fluorescently stained histopathological sections make it easier to identify amoebic pathogens.

CONCLUSION:Fluorescent staining technique is more sensitive to histopathological diagnosis of AK than HE staining and PAS staining, which can significantly improve the positive rate of detection of amoebic pathogens.