Occurrence of Gout in Rheumatoid Arthritis: It Does Happen!
Occurrence of Gout in Rheumatoid Arthritis: It Does Happen!
The cohort included 813 patients with incident RA between 1 January 1980 and 31 December 2007. The characteristics of the 813 patients are listed in Table 1. All patients were 18 years or older; there were 556 women (68%) and 257 men (32%). The mean age at diagnosis of RA was 55.9 years. The average length of follow-up was 9.6 years with 9771 total person-years. Rheumatoid factor was positive in 537 (66%) patients. A total of 627 (77%) patients had received corticosteroids, 737 (91%) had taken an NSAID for the treatment of RA sometime during their disease course and 349 (43%) used low-dose aspirin daily.
Out of the 813 patients with RA, 22 patients had coexisting gout and RA. The characteristics of these 22 patients are listed in Table 2. Mean age at the time of gout diagnosis was 69.6 years. Mean BMI of these patients was 33.4 kg/m. Rheumatoid factor and/or anticitrullinated protein was present in 14 out of 22 patients (64%). The mean uric acid level at the onset of gout was 8.2 mg/dl (normal reference ranges: male 4.3–8.0; female 2.7–6.1 mg/dl; information available for 17 out of 22 patients). The mean creatinine level at the onset of gout was 1.4 mg/dl (normal reference ranges: male 0.8–1.3; female 0.8–1.1 mg/dl; information available for 18 out of 22 patients). Diuretic use at onset of gout included nine (41%) out of 22 patients on thiazides and seven (32%) patients on furosemide. Recurrent attacks of gout was present in nine (41%) out of 22 patients and one (4%) out of 22 patients had a documented clinical history of tophi. The metatarsal phalangeal joint was involved in 12 (55%) cases, and urate crystals were identified in synovial fluid in nine (41%) patients.
Out of the 22 patients with coexistent gout and RA, six had gout prior to RA incidence date. Including these six with prevalent gout, the 25-year cumulative prevalence of gout diagnosed by clinical criteria in this cohort of patients with RA was 5.3% (95% CI: 2.0–8.6%) (Figure 1). Excluding the six with prevalent gout, the 25-year cumulative incidence of gout was 2.4% (95% CI: 1.1–3.6%). Including only the nine patients with crystal-proven gout attacks following RA incidence, the minimum 25-year cumulative incidence of gout diagnosed by clinical criteria was 1.3% (95% CI: 0.3–2.3%).
(Enlarge Image)
Figure 1.
Cumulative prevalence of gout among 813 patients with rheumatoid arthritis.
RA: Rheumatoid arthritis.
On 1 January 2008, the prevalence of gout in RA patients in Olmsted County was 1.9% (11 out of 582 patients). This is compared with the expected prevalence rate of 5.2% or 30 patients based on data from NHANES for the general population. The standardized prevalence ratio of observed to expected number of cases of gout (based on age- and sex-specific prevalence rates from NHANES) in RA was 0.36 (95% CI: 0.18–0.65), indicating gout in patients with RA was significantly less common compared with the general population.
Risk factor analyses were limited as the analysis could only be based on the 16 patients with RA who developed gout after the RA incidence. The risk factors for gout in RA were found to be older age (hazard ratio [HR]: 1.5 per 10-year increase; 95% CI: 1.03–2.18), male sex (HR: 3.18; 95% CI 1.12–8.99) and obesity (HR: 3.5; 95% CI: 1.12–10.91). The presence of erosions and/or destructive changes on radiographs was associated with a fourfold lower likelihood of developing gout (HR: 0.24; 95% CI: 0.07–0.88). Gout was more common among patients diagnosed with RA in recent years (1995–2007) than those diagnosed in earlier years (1980–1994; HR: 5.6; 95% CI: 1.60–19.57). Rheumatoid factor positivity (HR: 1.36; 95% CI: 0.49–3.78) and alcoholism (HR: 3.20; 95% CI: 0.86–11.91) were not significantly associated with the development of gout in RA in this cohort.
Results
The cohort included 813 patients with incident RA between 1 January 1980 and 31 December 2007. The characteristics of the 813 patients are listed in Table 1. All patients were 18 years or older; there were 556 women (68%) and 257 men (32%). The mean age at diagnosis of RA was 55.9 years. The average length of follow-up was 9.6 years with 9771 total person-years. Rheumatoid factor was positive in 537 (66%) patients. A total of 627 (77%) patients had received corticosteroids, 737 (91%) had taken an NSAID for the treatment of RA sometime during their disease course and 349 (43%) used low-dose aspirin daily.
Out of the 813 patients with RA, 22 patients had coexisting gout and RA. The characteristics of these 22 patients are listed in Table 2. Mean age at the time of gout diagnosis was 69.6 years. Mean BMI of these patients was 33.4 kg/m. Rheumatoid factor and/or anticitrullinated protein was present in 14 out of 22 patients (64%). The mean uric acid level at the onset of gout was 8.2 mg/dl (normal reference ranges: male 4.3–8.0; female 2.7–6.1 mg/dl; information available for 17 out of 22 patients). The mean creatinine level at the onset of gout was 1.4 mg/dl (normal reference ranges: male 0.8–1.3; female 0.8–1.1 mg/dl; information available for 18 out of 22 patients). Diuretic use at onset of gout included nine (41%) out of 22 patients on thiazides and seven (32%) patients on furosemide. Recurrent attacks of gout was present in nine (41%) out of 22 patients and one (4%) out of 22 patients had a documented clinical history of tophi. The metatarsal phalangeal joint was involved in 12 (55%) cases, and urate crystals were identified in synovial fluid in nine (41%) patients.
Out of the 22 patients with coexistent gout and RA, six had gout prior to RA incidence date. Including these six with prevalent gout, the 25-year cumulative prevalence of gout diagnosed by clinical criteria in this cohort of patients with RA was 5.3% (95% CI: 2.0–8.6%) (Figure 1). Excluding the six with prevalent gout, the 25-year cumulative incidence of gout was 2.4% (95% CI: 1.1–3.6%). Including only the nine patients with crystal-proven gout attacks following RA incidence, the minimum 25-year cumulative incidence of gout diagnosed by clinical criteria was 1.3% (95% CI: 0.3–2.3%).
(Enlarge Image)
Figure 1.
Cumulative prevalence of gout among 813 patients with rheumatoid arthritis.
RA: Rheumatoid arthritis.
On 1 January 2008, the prevalence of gout in RA patients in Olmsted County was 1.9% (11 out of 582 patients). This is compared with the expected prevalence rate of 5.2% or 30 patients based on data from NHANES for the general population. The standardized prevalence ratio of observed to expected number of cases of gout (based on age- and sex-specific prevalence rates from NHANES) in RA was 0.36 (95% CI: 0.18–0.65), indicating gout in patients with RA was significantly less common compared with the general population.
Risk factor analyses were limited as the analysis could only be based on the 16 patients with RA who developed gout after the RA incidence. The risk factors for gout in RA were found to be older age (hazard ratio [HR]: 1.5 per 10-year increase; 95% CI: 1.03–2.18), male sex (HR: 3.18; 95% CI 1.12–8.99) and obesity (HR: 3.5; 95% CI: 1.12–10.91). The presence of erosions and/or destructive changes on radiographs was associated with a fourfold lower likelihood of developing gout (HR: 0.24; 95% CI: 0.07–0.88). Gout was more common among patients diagnosed with RA in recent years (1995–2007) than those diagnosed in earlier years (1980–1994; HR: 5.6; 95% CI: 1.60–19.57). Rheumatoid factor positivity (HR: 1.36; 95% CI: 0.49–3.78) and alcoholism (HR: 3.20; 95% CI: 0.86–11.91) were not significantly associated with the development of gout in RA in this cohort.
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