Derivation of severity index for rheumatoid arthritis and its association with healthcare outcomes

Figures & data

Table 1.  Final indicators and associated scores from Delphi panel of study by Cabral et al.12.

	Rating 1 Mean (Range)
Radiology and Laboratory Findings
Presence of RF ever	2.7 (2–4)
Presence of HLA sub-type	3.0 (1–4)
C1-2 subluxation	5.2 (5–6)
Presence of CCP ever	3.0 (2–4)
Clinical and Functional Status Measures
Number of rheumatologist visits	3.2 (2–4)
Extra-articular Manifestations
Pulmonary nodules	3.5 (3–5)
Subcutaneous nodules	2.8 (2–4)
Vasculitis ever	5.0 (4–6)
Felty’s syndrome ever	5.0 (4–6)
Surgical History
Cervical spine fusion	5.5 (5–6)
Hand joint replacement	5.2 (4–6)
Foot joint replacement	4.2 (2–6)
Foot joint fusion	4.5 (2–6)
Ankle fusion	4.8 (3–6)
Wrist fusion	4.8 (3–6)
Total hip replacement	5.2 (4–6)
Total knee replacement	5.2 (4–6)
Elbow replacement	5.3 (4–6)
Shoulder replacement	5.5 (5–6)
Medications
Any oral glucocorticoid use	2.8 (2–4)
Intra-articular glucocorticoids	2.7 (2–4)
Maximum glucocorticoid dose	3.8 (3–5)
Disease-modifying Anti-rheumatic Drugs
Azathioprine	4.2 (3–5)
Cyclosporin	4.5 (4–5)
Gold	2.3 (2–3)
Hydroxychloroquine	2.0 (2)
Leflunomide	3.8 (3–4)
Methotrexate	3.8 (3–4)
Sulfasalazine	2.3 (2–3)
Biologic Therapies
Adalimumab	4.2 (4–5)
Infliximab	4.0 (3–5)
Etanercept	4.2 (4–5)
Kineret	4.8 (4–5)
Combination Therapy (Any 2 DMARDs or Biologics concurrently)	3.8 (3–4)

RF, rheumatoid factor; HLA, human leukocyte antigen; C1-2, cervical spine 1-2; CCP, anti-cyclic citrullinated peptide.

For new biologic therapies approved since the ‘Delphi panel’, we applied averaged scores depending on class. For golimumab, certolizumab pegol, and average of tumor necrosis factor (TNF) blockers, a rating of 4.13 was applied; for abatacept, rituximab, and tocilizumab, a mean value of anakinra (4.8) was applied.

Table 2.  SIFRA scores without laboratory distribution.

Variable	n	Mean	Min	Max	Median	STD
SIFRA without laboratory data (SIFRA1)	25,042	9.14 (100%)	0	160	7	8.77
Clinical & functional status	25,042	5.60 (61.29%)	0	160	3.2	6.41
Extra-articular manifestations	25,042	0.19 (2.10%)	0	11.3	0	0.88
Surgical history	25,042	0.05 (0.50%)	0	10.3	0	0.51
Medications	25,042	3.30 (36.12%)	0	23.1	3.8	3.71

Table 3.  SIFRA scores with laboratory distribution.

Variable	n	Mean	Min	Max	Median	STD
SIFRA with laboratory data (SIFRA1)	23,951	10.02 (100%)	0	160	9.1	8.89
Radiology & laboratory findings	23,951	0.56 (5.55%)	0	8.7	0	1.16
Clinical & functional status	23,951	5.83 (58.16%)	0	160	3.2	6.44
Extra-articular manifestations	23,951	0.20 (1.97%)	0	11.3	0	0.89
Surgical history	23,951	0.05 (0.48%)	0	10.3	0	0.52
Medication	23,951	3.39 (33.84%)	0	23.1	3.8	3.73

STD: standard deviation; SIFRA: Severity Index for Rheumatoid Arthritis

Table 4.  Spearman’s rank correlation of SIFRA score with previously validated severity score.

Score	CIRAS
	n	Spearman	95% CI		p-value
SIFRA without laboratory data	25,042	0.5252	0.5162	0.5341	< 0.0001
SIFRA with laboratory data	23,951	0.5392	0.5302	0.5482	<0.0001
Sub-groups—SIFRA without laboratory data
Age
<65 years	12,411	0.6148	0.6037	0.6256	<0.0001
≥65 years	12,631	0.6846	0.6752	0.6937	<0.0001
Gender
Male	22,658	0.5400	0.5307	0.5492	<0.0001
Female	2384	0.4591	0.4267	0.4901	<0.0001
Sub-groups—SIFRA with laboratory data
Age
<65 years	12,007	0.6242	0.6131	0.6349	<0.0001
≥65 years	11,944	0.6886	0.6790	0.6979	<0.0001
Gender
Male	21,662	0.5531	0.5438	0.5623	<0.0001
Female	2289	0.4734	0.4409	0.5045	<0.0001

CI, confidence interval; SIFRA, Severity Index for Rheumatoid Arthritis; CIRAS, claims-based index for rheumatoid arthritis severity

Figure 1.  SIFRA scores and total healthcare costs.

Figure 2.  SIFRA dcores and RA-related healthcare costs.

Figure 3.  SIFRA scores and healthcare visits.

Table 5.  Correlation of SIFRA with commonly-used comorbidity scores in RA outcomes research.

Index	Spearman	95% CI		p-value
SIFRA without Laboratory Data
Elixhauser Index	0.1052	0.0929	0.1174	<0.0001
Charlson Comorbidity Index	0.1503	0.1382	0.1624	<0.0001
Chronic Disease Score	0.2548	0.2427	0.2668	<0.0001
SIFRA with Laboratory Data
Elixhauser Index	0.0793	0.0667	0.0919	<0.0001
Charlson Comorbidity Index	0.1135	0.1009	0.1260	<0.0001
Chronic Disease Score	0.2393	0.2270	0.2516	<0.0001

CI, confidence interval; SIFRA, Severity Index for Rheumatoid Arthritis

Table 6.  Additional percentage of variation explained by adding SIFRA to outcomes models.

	CCI + SIFRA	CDS + SIFRA	ELIX + SIFRA
SIFRA with Laboratory Scores
Total costs	104%	54%	156%
Total number of visits	25%	8%	44%
RA-related total costs	611%	429%	601%
RA-related total number of visits	642%	502%	619%
SIFRA without Laboratory Scores
Total costs	96%	51%	141%
Total number of visits	22%	6%	39%
RA-related total costs	528%	361%	532%
RA-related total number of visits	596%	454%	569%

SIFRA, Severity Index for Rheumatoid Arthritis; CCI, Charlson Comorbidity Index; CDS, Chronic Disease Score; ELIX, Elixhauser Index.

Models are controlled for age, gender, and comorbid conditions. Percentage increases in adjusted R² are present when SIFRA is added to the model.

Cabral D, Katz JN, Weinblatt ME, et al. Development and assessment of indicators of rheumatoid arthritis severity: results of a delphi panel. Arthritis Rheum 2005;53:61-6

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