Table 1.

Model parameters

Variables	Base case parameter value	Reference
Population of Ireland	4 857 000	[28]
Overall incidence of RA in the population	0.00032	[29]
Probability of individual having inflammatory arthritis or non-inflammatory arthritis	0.5	[21]
Probability an individual with UA presents to the A&E	0.2	[14]
Probability an individual with UA who presents to the A&E obtains a referral to a rheumatologist	1	[21]
Probability of presenting to a GP within 3 months of symptom onset	0.4	[21]
Probability of presenting to a GP outside of 3 months of symptom onset	0.6	1–# from above
Probability of being referred to the rheumatologist first time upon first GP visit under the CPr	0.2	[30]
Probability of being referred to the rheumatologist after a further three GP visits under the CPr	0.8	1–# from above
Probability of being referred to the rheumatologist first time upon first GP visit under the EIM	0.8	[21]
Probability of being referred to the rheumatologist after a further three GP visits under the EIM	0.2	1–# from above
Probability of being diagnosed by a rheumatologist within 3 months of symptom onset once referred under the CPr	0.4	[21] with a range of 0.33–0.51
Probability of being diagnosed by a rheumatologist within 3 months of symptom onset once referred under the EIM	0.51	[21] with a range of 0.4–0.57
Probability of a GP carrying out a RF testa	0.49	[21]
Probability of a GP carrying out a CRP testa	0.56	[21]
Probability of a GP carrying out an ESR testa	0.60	[21]
Probability of a GP carrying out an anti-CCP testa	0.12	[21]
Probability of a GP carrying out a full blood count testa	0.75	[21]
Probability of a GP carrying out an X-raya	0.09	[21]
Probability of a rheumatologist carrying out a RF test	0.6	[21]
Probability of a rheumatologist carrying out an anti-CCP test	0.68	[21]
Probability of a rheumatologist carrying out an X-ray	0.69	[21]
Probability of a rheumatologist/GP carrying out the above tests on non-inflammatory arthritis patients	0.5	[21]

^aOnly individuals who were not referred upon their first GP visit have tests carried out by the GP before referral to a rheumatologist. A&E: Accident and Emergency; CPr: current practice; EIM: early identification and referral model; GP: general practitioner; UA: undifferentiated arthritis.