Autoantibody detection: prevailing practices at a tertiary care hospital in Riyadh

Anti-nuclear antibody (ANA) test as the first level investigation for detection of auto-immune rheumatic disease has been recommended in a number of international guidelines. This study was performed to evaluate the local practice and trends of auto-antibody laboratory requests.

Data were collected from 249 initial laboratory requests for first level auto-antibody detection between April 2012 and April 2013 in the Immunology Unit at King Khalid University Hospital, Riyadh. This group of patients included 151 females and 98 males (mean age 40.1 +/- 21; range 4-85 years).

Of the total requests, ANA as a single first level investigation was requested by only 32 (13%) clinicians whereas the rest of the investigations included simultaneous testing of ANA and second level extractable nuclear antigen (ENA) auto-antibody tests. Anti-double stranded DNA (anti-dsDNA) antibody was simultaneously tested with ANA in 158 patients as first level test where both the tests were positive in 44 (27.8%) patients and in 24 (15.1%) patients a negative ANA test was associated with a positive anti-dsDNA antibody test. Rheumatoid factor (RF) tested positive in 04/53 (7.5%), anti-neutrophil cytoplasmic antibody (ANCA) in 01/48 (2%) and SS-A and SS-B in 03/37 (8.1%) requests as first level tests with ANA.

Using second level auto-antibody tests in conjunction with ANA as the first line investigation does not appear to be a cost effective approach, highlighting the importance of adherence to the guidelines. ANA negative and anti-dsDNA positive group of patients requires further assessment in a large scale study.