Clinical decision rules in rheumatoid arthritis: do they identify patients at high risk for osteoporosis? Testing clinical criteria in a population based cohort of patients with rheumatoid arthritis recruited from the Oslo Rheumatoid Arthritis Register. (Extended Report).

Background: Preliminary clinical criteria based on age, inflammation, and immobility have been proposed to identify which patients with rheumatoid arthritis (RA) should be examined by dual energy x ray absorptiometry (DXA) to diagnose osteoporosis. The three item criteria have not been evaluated in male patients with RA or in the entire female RA population.

Objectives: (1) To test the proposed criteria in a cohort of men and women thought to be representative of the entire underlying RA population. (2) To develop clinical decision rules, which could be applied to all patients with RA irrespective of corticosteroid use.

Methods: Clinical and demographic data were collected from a total of 287 representative patients with RA (235 (82%) women, 52 (18%) men, age range 25.3-73.1 years) from the Oslo RA register (completeness 85%). Bone mineral density (BMD) was measured in spine L2-4 (anterior-posterior view) and femoral neck by DXA. The criteria were applied and sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.

Results: Mean age (SD) for the women and men with RA was 56.8 (11.0) years and 61.5 (10.2) years; disease duration was 15.5 (9.5) years and 14.7 (8.6) years. Of the women 163 (69%) were postmenopausal. One hundred and seventeen (50%) women and 28 (54%) men fulfilled the three item criteria. For the diagnosis of osteoporosis (T score [less than or equal to] -2.5) using the original three item criteria sensitivity in women and men was 74% and 67%, specificity 57% and 50%, PPV 32% and 29% and NPV 89% and 83%, and including weight and ever use of corticosteroids in a five item criteria sensitivity increased to 82% and 83%, specificity decreased to 45% and 45%, PPV was 29% and 31%, and NPV was 90% and 90% respectively.

Conclusion: The novel five item criteria (age, weight, inflammation, immobility, and ever use of corticosteroids) are a more accurate tool to identify patients with RA and osteoporosis than the original three item criteria (age, inflammation, and immobility). The clinical decision rules have an acceptable sensitivity and provide a practical tool for the doctor to identify patients with RA who should have a DXA measurement performed.

**********

In the rheumatoid arthritis (RA) population osteoporosis is more often found than in the normal population, (1 2) and both inflammation, decreased functional capacity, (3 4) and corticosteroids (5) have been identified as independent risk factors for osteoporosis.

Dual energy x ray absorptiometry (DXA) is the gold standard for assessing bone density, and the World health Organisation (WHO) definition of osteoporosis is based on this. (6) In clinical practice, patients with RA with reduced bone density or osteoporosis could be identified either by a screening method or by a case identifying strategy measuring only patients at increased risk for osteoporosis. Although bone densitometry is the method of choice for detecting low bone density, its use may be limited by the availability of equipment, cost, and reimbursement issues. Valid decision rules to identify patients with RA at high risk for osteoporosis based on demographic and clinical risk factors could therefore be of clinical importance by targeting the use of DXA to patients with a high probability of having osteoporosis. For osteoporosis induced by corticosteroids separate guidelines have been published. (7)

Preliminary criteria to identify patients at increased risk of having osteoporosis based on age (women > 50 years and men >60 years), disease activity (persistently increased C reactive protein (CRP) [greater than or equal to] 20 mg/l, or erythrocyte sedimentation rate (ESR) [greater than or equal to] 20 mm/1st h), or both and functional status (Steinbrocker score [greater than or equal to] 3 or Health Assessment Questionnaire (HAQ) score [greater than or equal to] 1.25) have been proposed by Lems and Dijkmans. (8) Patients who fulfilled two out of three of the above criteria were considered to require a DXA bone density measurement at hip and spine to diagnose osteoporosis. The criteria have recently been tested by NoUa et al (9) in a series of consecutive postmenopausal patients with RA attending an outpatient clinic. The proposed criteria have so far not been tested in patients with RA thought to be representative of the entire RA population. In male patients with RA the criteria have not been tested at all.

The first aim of this study was to evaluate the proposed three item criteria in a cohort of men and women with RA suggested to be representative of the entire RA population. The second aim was to examine modified versions of the proposed criteria including weight (1 2) and the use of corticosteroids, (10 11) both well known risk factors for osteoporosis in patients with RA, in an attempt to develop decision rules which could be applied to all patients with RA irrespective of corticosteroid use.

METHODS

Study population

We have previously published cross sectional data on bone mineral density (BMD) and risk factors for osteoporosis in 394 women (1) and 94 men (2) with RA, age 20-70 years, recruited from the Oslo RA register, validated to be complete at the 85% level. (12) As previously described, the examined women were representative (1) and the men (2) fairly representative compared with the register population. At that time neither the HAQ nor the Steinbrocker score was used, which made it impossible to precisely test the proposed criteria by Lems and…