Tear and saliva ferning tests in Sjögren's syndrome (SS)

The purpose of this study was to evaluate the tear ferning test (TFT) and the saliva ferning test (SFT) as diagnostic tests for xerophthalmia and xerostomia respectively in patients with SS. Dried samples of freshly produced tears and saliva from: (A) 36 healthy controls without sicca symptoms, (B) 61 patients with primary SS, (C) 53 patients with secondary SS and (D) 22 patients with psychiatric disorders receiving antidepressants, were examined by polarizing light microscopy. All individuals included in the study were postmenopausal women. The crystallization was classified into 4 types according to the ferning phenomenon: uniformity, branching, spreading and integrity (type I normal and II, III, IV abnormal). Abnormal TFT was found in tear samples of: (A) 8/72 normal control eyes, (B) 110/122 prim SS eyes, (C) 86/106 sec SS eyes and (D) 30/44 psychiatric patients' eyes. Abnormal SFT was found in: (A) 6/36 of normal controls, (B) 59/61 of prim SS, (C) 51/53 of sec SS patients and (D) 16/22 of psychiatric patients. The differences of both TFT and SFT of patients with prim SS and sec SS versus controls were significant (p < 0.001). The sensitivity of TFT was found to be high both in prim SS (90%) and in sec SS (81%). In addition the specificities of TFT and SFT were high 89% and 83% respectively. On the other hand the differences of TFT and SFT in psychiatric patients receiving antidepressants versus normal controls were also significant (p < 0.05 and p < 0.025 respectively). According to our data TFT and SFT are simple, sensitive and specific tests to evaluate xerophthalmia and xerostomia in SS and probably in other conditions characterized by mucous membrane dryness.