The Incidence and Predictors of Infection in Psoriasis and Psoriatic Arthritis: Results from Longitudinal Observational Cohorts

Amir Haddad; Suzanne Li; Arane Thavaneswaran; Richard J. Cook; Vinod Chandran; Dafna D. Gladman

doi:10.3899/jrheum.140067

Article Figures & Data

Figures

Tables

Download figure
Open in new tab
Download powerpoint
Figure 1.
Patient disposition. PsA: psoriatic arthritis; PsC: psoriasis without arthritis.

Tables

Figures

View popup

Table 1.

Characteristics of all patients with PsA and PsC at first visit since 2006. Values are mean (SD) unless otherwise specified.

Variables	PsA, n = 695	PsC, n = 509
Sex, n (%)
Female	294 (42)	219 (43)
Male	401 (58)	290 (57)
Race, n (%)
White	601 (86)	391 (77)
Other	94 (14)	118 (23)
Age at study, yrs	49.5 (13.3)	46.5 (13.1)
Age at diagnosis of psoriasis, yrs	28.1 (14.4)	30.3 (16.2)
Age at diagnosis of PsA, yrs	37 (13.1)	—
Duration of psoriasis, yrs	21.5 (13.6)	16.2 (14)
Duration of PsA, yrs	12.5 (11.1)	—
Alcohol, n (%)
Daily	52 (8)	56 (11)
None	287 (42)	148 (29)
Social	351 (51)	305 (60)
Smoking status, n (%)
Current	91 (13)	126 (25)
No	370 (53)	232 (46)
Past	233 (34)	151 (30)
Presence of nail lesions, n (%)	430 (62)	248 (49)
PASI score	4.9 (7.4)	5.6 (5.8)
Active SJC or TJC	6.7 (9.2)	—
SJC	1.2 (2.5)	—
TJC	4.2 (7)	—
Damaged joint count	7 (12.1)	—
Body mass index, kg/m²	29.3 (6.5)	27.9 (5.7)
Diabetes, n (%)	69 (10)	35 (7)
Congestive heart failure, n (%)	5 (1)	0 (0)
Chronic obstructive lung disease, n (%)	2 (0.003)	0 (0)
Liver disease, n (%)	19 (3)	6 (1)
Cancer, n (%)	27 (4)	23 (5)
Use of NSAID, n (%)	419 (60)	18 (4)
Use of DMARD, n (%)	391 (56)	50 (10)
Use of biologics, n (%)	160 (23)	22 (4)
Ultraviolet light therapy, n (%)	112 (16)	398 (78)
Presence of axial disease, n (%)	385 (55)	—
Steinbrocker score	8.1 (18.6)	—

PsA: psoriatic arthritis; PsC: psoriasis without arthritis; PASI: Psoriasis Area and Severity Index; SJC: swollen joint count; TJC: tender joint count; NSAID: nonsteroidal antiinflammatory drugs; DMARD: disease-modifying antirheumatic drugs.

View popup

Table 2.

Characteristics of infections observed in both cohorts. Values are n (%) unless otherwise specified.

Characteristics	PsA	PsC	p
Total no. infections	498	74
Infection type			0.057
Bacterial	312 (63)	56 (76)
Viral	167 (34)	15 (20)
Other	19 (4)	3 (4)
Infection site			0.001
Gastrointestinal	11 (2)	4 (6)
Genitourinary	66 (14)	11 (15)
Lung	105 (23)	9 (12)
Sinus	58 (13)	5 (7)
Skin	72 (16)	14 (19)
Unknown	21 (5)	4 (6)
Upper respiratory	47 (10)	0 (0)
Other	83 (18)	25 (35)
Treatment of infection with antibiotics	313 (63)	57 (77)	0.019
Type of antibiotics			0.22
Intravenous	24 (8)	1 (2)
Oral	280 (89)	55 (96)
Both	9 (3)	1 (2)
Infection requiring hospitalization	10 (2)	2 (3)	0.66

PsA: psoriatic arthritis; PsC: psoriasis without arthritis.

View popup

Table 3.

Multivariate analysis of predictors of infection in the PsC and PsA cohorts. OR > 1 indicate higher risk. OR < 1 indicate reduced risk.

Variable	PsA		PsC
Variable	OR (95% CI)	p	OR (95% CI)	p
Disease duration, yrs	1.00 (0.99–1.01)	0.875	1.01 (0.99–1.03)	0.454
Male vs female	0.47 (0.36–0.61)	< 0.0001	1.03 (0.58–1.82)	0.928
PASI, 1-unit increase	1.00 (0.98–1.02)	0.978	0.92 (0.86–0.98)	0.009
Active joint count, 1-unit increase	1.00 (0.99–1.02)	0.900	NA	NA
Biologics, yes vs no	1.70 (1.33–2.18)	< 0.0001	2.14 (0.88–5.20)	0.09
DMARD, yes vs no	1.15 (0.91–1.47)	0.244	1.28 (0.57–2.86)	0.58
NSAID, yes vs no	1.06 (0.82–1.37)	0.654	1.20 (0.44–3.28)	0.72
Ultraviolet therapy	0.37 (0.18–0.74)	0.005	0.44 (0.23–0.84)	0.01
FCI	1.08 (0.98–1.18)	0.114	1.27 (1.02–1.59)	0.04

PsC: psoriasis without arthritis; PsA: psoriatic arthritis; PASI: Psoriasis Area and Severity Index; DMARD: disease-modifying antirheumatic drugs; NSAID: nonsteroidal antiinflammatory drugs; FCI: Functional Comorbidity Index; NA: not applicable.

View popup

Table 4.

Predictors of time to first infection since 2006 for the PsC and PsA cohorts. An HR < 1 means that the risk of infection is lower than when the covariate is at the reference level.

Variable	PsA		PsC
Variable	HR	p	HR	p
Disease duration, yrs	0.99	0.32	0.99	0.51
Active joint count, 1-unit increase	1.01	0.13	NA	NA
Male vs female	0.63	0.0004	0.91	0.71
PASI, 1-unit increase	0.99	0.20	0.99	0.75
FCI	1.18	0.002	1.37	0.02
Biologics, yes vs no	1.61	0.001	1.32	0.73
NSAID, yes vs no	1.19	0.20	1.37	0.67
DMARD, yes vs no	1.05	0.73	0.66	0.44
Ultraviolet therapy	1.25	0.29	0.73	0.33

PsC: psoriasis without arthritis; PsA: psoriatic arthritis; PASI: Psoriasis Area and Severity Index; FCI: Functional Comorbidity Index; NSAID: nonsteroidal antiinflammatory drugs; DMARD: disease-modifying antirheumatic drugs; NA: not applicable.