Antinuclear antibody titration and pattern are helpful in the diagnosis of systemic autoimmune rheumatic diseases.

INTRODUCTION: Anti-nuclear antibody (ANA) testing is among the most common immunological test requested in the diagnostic immunology laboratory. The main purpose of this test is to screen for the underlying systemic autoimmune rheumatic diseases (SARDs). The gold standard laboratory method for ANA detection is by the indirect immunofluorescence (IIF) assay. In most laboratories, positive ANA-IIF is reported in terms of titration and pattern. OBJECTIVE: This study was conducted with the aim of determining the correlation between ANA-IIF titration and pattern for the diagnosis of SARDs. MATERIALS AND METHODS: A retrospective study was conducted whereby the positive ANA-IIF samples from 1st July 2018 until 31st December 2019 and 1st January 2021 until 31st March 2021 were included in this study. The duplicate samples were excluded. ANA-IIF titration and pattern were recorded for all patients. The demographic, clinical, and final diagnosis data were retrieved from each patient's clinical note. RESULTS: A total of 179 patients were included for analysis. The majority of the patients were female (79.9%) and from Malay ethnicity (66.5%). Sixty-five patients (36.3%) had ANA-IIF positive at 1:80 titration followed by 45 patients (25.1%) positive at titration of equal or more than 1:160. Speckled was the predominant pattern visualised in 90 patients (50.3%) followed by homogeneous in 76 patients (42.5%). Forty-five patients (25.1%) were finally diagnosed with SARDs with 41 of them diagnosed as SLE. ANA titration was significantly associated with the final diagnosis of SARDs at all titres (p<0.001) but the best cut-off was noted at a titre of equal or more than 1:320 with the sensitivity and specificity of 86.7% and 77.6% respectively. The homogeneous pattern was also significantly associated with SARDs (p=0.04). The final diagnosis of SARDs were significantly higher in female (p=0.03) and their age was significantly younger (p<0.001). CONCLUSION: ANA-IIF titration of equal or more than 1:320 can be used as the best titration for differentiating between SARDs and non-SARDs in a positive ANA sample. Patients with homogeneous pattern were more likely to be diagnosed with SARDs than other ANA-IIF patterns.

The recognition of anti-nuclear antibody's dense fine speckled pattern and the detection of anti-DFS70 antibodies in the laboratory practice: Its prevalence and clinical significance.

Anti-nuclear antibody test (ANA) is the test commonly requested for the working diagnosis of systemic autoimmune rheumatic diseases (SARDs) particularly in ANA-associated rheumatic diseases (AARDs) such as SLE, systemic sclerosis, Sjogren syndrome, mixed connective tissue diseases, and dermatomyositis. Dense fine speckled (DFS) pattern is an ANA fluorescence pattern that is commonly encountered in laboratories. This pattern is largely detected among the healthy population and in non-SARDs patients. Although this pattern is still can be observed among SARDs patients, the low prevalence of monospecific or isolated anti-DFS70 antibodies makes it useful for ruling out AARDs diagnosis. Thus, the inclusion of anti-DFS70 antibodies is perhaps logical for the exclusion of SARDs/AARDs. This review provides evidence of the prevalence of anti-DFS70 antibodies in different populations including healthy individuals, patients with SARDs and non- SARDs. The algorithm that includes the detection of anti-DFS70 antibodies during ANA screening is also suggested.