P92 Referral with a positive antinuclear antibody? Lessons from prospective triage and diagnosis in a single-centre service evaluation of 1,547 new rheumatology referrals
Authors: Cleaton Natasha , Bateman James 
Published: April 2020

Abstract

Background
Blood tests assessing for the presence of antinuclear antibodies (ANA) are frequently used as a screening method for ANA-associated rheumatic disease (AARD), including systemic lupus erythematosus (SLE), systemic sclerosis (SSc), undifferentiated connective tissue disease (UCTD), and Sjögren's syndrome (SjS). Past research suggests a positive ANA makes up between 4 and 17% of new rheumatology referrals, however little is known about how more detailed referral information can be used to triage these referrals. This service evaluation explores how ANA and clinical referral data relate to the final diagnoses.

Methods
New out-patient referrals to a single consultant rheumatologist at one UK centre were prospectively coded, over a 40-month period (04/16-08/19), prior to clinical assessment. Data collected included anonymised baseline demographics, referral source, summarised by ‘key referral features’ [ANA testing; number of AARD flags e.g. Raynaud’s (RP), serositis, photosensitivity, inflammatory markers], and diagnosis after assessment. Referral text was coded using up to four 4 ‘key-features’ in line with established clinical reasoning theory (e.g. polyarthralgia, fatigue, synovitis, raised inflammatory markers). The assessment diagnosis was coded against established rheumatological diagnostic categories, with a separate code for awaiting investigations. The data was anonymised, password protected, and analysed for the service evaluation.

Results
Of the 1,748 referrals, 177 (10.1%) were excluded because of incomplete data, leaving 1547 for analysis. Of these patients 76(5%) were ANA+, with no prior diagnosis of a AARD. The ANA+ 76 were middle aged (mean 56years; SD 14.6years), and predominantly female (60/76). The main referrers were primary care (56/76) and haematology (8/76), the remainder from eight secondary care specialities and extended-scope-physiotherapy. The majority (58/78,76%) had non-inflammatory diagnosis (e.g. osteoarthritis); 9 (12%) were diagnosed AARD (SLE,3; SjS,2; SSc,3; UCTD,1); 9 had other inflammatory disease (gout,3; PMR,1; reactive,1; undifferentiated inflammatory arthritis,4). The AARD flags prospectively coded from the initial referral, prior to assessment, in ANA+ patients were as follows: 0 flags (e.g. ANA+, fatigue, arthralgia), 1/43 patients had AARD (2.3%); 1 flag, 5/29 AARD (17.2%); 2 flags 1/3 AARD (33%); 3 flags 1/1 AARD (100%). Of the 1,471/1,546 referrals with no ANA test, 3 were diagnosed as a AARD (UCTD,1 ; SLE,2).

Conclusion
This service evaluation shows ANA positive referrals account for 5% of new referrals to our centre, and is the first to our knowledge to evaluate ANA positive referrals based on prospective AARD flags from the referral to evaluate the likelihood of a CTD. Many referrals from the cohort diagnosed with a new CTD had prior ANA testing (75%). These data can potentially help to train and educate specialists in ANA requesting when referring to rheumatology, and assist other departments implementing AARD flags to triage referrals.

Disclosures
N. Cleaton None. J. Bateman None.