Comparison of fluorescence staining and periodic acid-Schiff staining in the diagnosis of fungal keratitis

Objective

To compare the effect of fluorescence staining and periodic acid-Schiff staining in the diagnosis of fungal keratitis (FK).

Methods

A total of 147 corneal specimens from 147 FK patients treated in Eye Hospital of Shandong First Medical University from January 2017 to May 2019 with positive corneal scraping or fungal culture were collected.Among them, there were 84 cases with penetrating keratoplasty (PKP), 42 cases with lamellar keratoplasty (LKP) and 21 cases with lesion resection.Another 11 cases with herpes simplex virus keratitis served as negative control.The corneal tissue specimens were performed with fungal fluorescence staining and periodic acid-Schiff staining, respectively.The stained sections were placed under fluorescence microscope and optical microscope to observe fungal hyphae or spores, respectively.The positive rates of the two staining methods were compared, and the positive cases of the diagnosis of FK in corneal tissue samples obtained by different surgical methods and corneal infection caused by different strains of the two staining methods were compared.Written informed consent was obtained from each patient.The study protocol adhered to the Declaration of Helsinki and was approved by the Ethics Committee of Shandong Eye Hospital (No.SDSYKYY-2016012).

Results

The positive rate of periodic acid-Schiff staining and fungal fluorescence staining was 60.5% (89/147) and 79.6% (117/147), respectively.The positive rate of fluorescence staining in the diagnosis of fungal keratitis was significantly higher than that of periodic acid-Schiff staining (χ²=28.00, P<0.01), and both the specificity of the two staining methods was 100%.The positive rate of specimens obtained by PKP with fluorescent staining was 85.7% (72/84), and the positive rate with periodic acid-Schiff staining was 65.5% (55/84), and the difference was statistically significant (χ²=17.00, P<0.01). The positive rate of specimens obtained by LKP with fluorescent staining was 71.4% (30/42), and the positive rate with periodic acid-Schiff staining was 52.4% (22/42), and the difference was statistically significant (χ²=8.00, P<0.01). The positive rate of resected foci specimens with fluorescent staining was 71.4% (15/21), and the positive rate with periodic acid-Schiff staining was 57.1% (12/21), and the difference was not statistically significant (χ²=1.30, P=0.25). The positive cases of two kinds of staining were different among different fungal strains.Among them, the positive cases of Fusarium solani complex, Pythium insidiosum, Aspergillus fumigatus complex, Candida guilliermondii, Trichoderma and Nigrograna mackinnonii with fluorescence staining were 19, 5, 5, 1, 1 and 1, and the positive cases of periodic acid-Schiff staining were 11, 0, 3, 0, 0 and 0, respectively.The staining results of the 11 negative controls were negative.

Conclusions

Fluorescence staining is more sensitive than periodic acid-Schiff staining in the detection of fungal components in paraffin-embedded corneal tissues, and it can significantly improve the fungal detection rates.

Fluorescence staining; Fungal keratitis; Histopathology; Diagnosis