Assessment of ideal serum dilution for screening of antinuclear antibodies by an indirect immunofluorescence method in diagnosis of autoimmune disorders

BACKGROUND

Time and cost constraints lead to majority of clinical laboratories deviating away from an ideal practice of checking for antinuclear antibodies (ANAs) by indirect immunofluorescence (IIF) at multiple dilutions. Usage of screening dilution of 1:40 recommended by most manufacturers of commercial ANA kits results in numerous false positive-tests and misdiagnosis of connective tissue disorders (CTDs). We sought to study the ideal screening dilution for ANA by IIF for a diagnosis of ANA-related CTDs.

METHODS

Serum samples of patients with ANA-related conditions (n = 233) and healthy controls (n = 154) were evaluated by IIF using Immuno Concepts Hep-2000 ® ANA kits at dilutions from 1:40 to 1:640. Accuracy for diagnosis of CTDs for each serum dilution was assessed by receiver operating curve (ROC) analysis.

RESULTS

Antinuclear antibodies (ANA) positivity was observed in 19.5%, 10.4%, 4.55%, 0.65%, and 0% of healthy controls at dilutions of 1:40, 1:80, 1:160, 1:320, and 1:640, respectively. ANA positivity at 1:40 dilution was observed among 26.4% cases with mimics of CTDs. Prevalence of ANA positivity in ANA-related CTDs was 97.3%, 96.4%, 89.3%, 83.9%, and 71.4% at dilutions of 1:40, 1:80, 1:160, 1:320, and 1:640, respectively. ROC analysis revealed best test performance for distinction between healthy and ANA-related CTD populations at a serum dilution of 1 in 80.

CONCLUSIONS

Antinuclear antibodies (ANA) positivity at low titers (1:40) is highly prevalent in healthy population (19.5%) as well as amongst mimics of CTD (26.4%). Our study suggests a higher screening dilution of 1:80 for ANA by IIF for diagnosis of CTD maybe better. Combination of 1:80 and 1:160 dilutions provides optimum sensitivity and specificity for diagnosis of ANA-related disorders.

Pattern of antinuclear antibody and antiextractable nuclear antigen antibody test requisitions in Riyadh

Background:

International guidelines for screening of systemic autoimmune rheumatic diseases (SARD) recommend antinuclear antibody (ANA) test as the first level test and antiextractable antigen (anti-ENA) along with anti-double-stranded DNA (anti-dsDNA) as second line tests following a reactive ANA test. This study was performed to assess adherence to international guidelines for investigation of SARD and to compare the requesting pattern of ANA and second level tests between rheumatology and nonrheumatology physicians in Riyadh.

Methodology:

This retrospective cross-sectional study comprising of 300 first time requests for investigation of SARD was performed in the immunology unit at King Khalid University Hospital (KKUH). Data were collected between April and May 2018. Information regarding the requesting physicians’ specialty and the first time requested tests (ANA, anti-dsDNA, and anti-ENA) were extracted from the electronic medical records. Reasons for requisition of tests were also recorded.

Results:

Of the total requests, 159 (53%) requests included ANA as a single first level test, whereas the rest of the requests (n = 141, 47%) included ANA test in conjunction with second level tests for the investigation of SARD. From the department of rheumatology, 14 (29.8%) initial requests were for ANA test as the only first line investigation that was significantly lower than 145 (57.3%) similar requests from the rest of the departments (P < 0.001).

Conclusion:

ANA and second level tests requests by physicians particularly among rheumatologists lacked compliance to international guidelines. The current study strongly suggests the need for strict compliance to international guidelines for screening of systemic autoimmune disorders among physicians.

Eosinophilic Granulomatosis With Polyangiitis With Thrombotic Microangiopathy: Is Simultaneous Systemic Lupus Erythematosus Associated With Clinical Manifestations?: A Case Report and Review of the Literature

Eosinophilic granulomatosis with polyangiitis (EGPA) is one of the antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, which is characterized by vasculitis of the small to medium-sized vessels. On the contrary, thrombotic microangiopathy (TMA) is a life-threatening condition which can cause ischemic organ injury. Although several case reports have described patients with TMA associated with ANCA-associated vasculitis except for EGPA, there are no previous case reports of EGPA associated with TMA.A 71-year-old Japanese man was diagnosed with EGPA based on his asthma, eosinophilia, lung opacity, refractory sinusitis, and positive myeloperoxidase-ANCA. He was also diagnosed with TMA based on peripheral schizocytes and hemolytic anemia. We performed plasmapheresis and started high-dose corticosteroid therapy; thereafter, he improved promptly. His case also fulfilled the classification criteria of systemic lupus erythematosus (SLE) based on the pleural effusion, renal disorder, anemia, thrombocytopenia, positive antidouble-stranded DNA antibody, and low complement. Elements of SLE were thought to affect his clinical course.We reviewed 11 patients with EGPA or hypereosinophilic syndrome (HES) associated with SLE, including our case. Patients with EGPA or HES associated with SLE had more heart complications than patients with simple EGPA or simple HES did. Patients with EGPA or HES associated with SLE had more pleural effusion than patients with simple SLE did.Clinical manifestations of eosinophilia with SLE or SLE with eosinophilia may differ from simple SLE or simple eosinophilia.