Development and initial validation of a self-assessed lupus organ damage instrument.
OBJECTIVE
The Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) is a validated instrument for assessing organ damage in systemic lupus erythematosus (SLE). Trained physicians must complete it, thus limiting utility where this is impossible.


METHODS
We developed and pilot tested a self-assessed organ damage instrument, the Lupus Damage Index Questionnaire (LDIQ), in 37 SLE subjects and 7 physicians. After refinement, 569 English-speaking SLE subjects and 14 rheumatologists from 11 international SLE clinics participated in validation. Subjects and physicians completed the instruments separately. We calculated sensitivity, specificity, Spearman's correlations, and agreement using the SDI as the gold standard. Six hundred five SLE participants in the community-based National Data Bank for Rheumatic Diseases (NDB) study completed the LDIQ and we assessed correlations with outcome and disability measures.


RESULTS
The mean LDIQ score was 3.3 (range 0-16) and the mean SDI score was 1.5 (range 0-9). The LDIQ had a moderately high correlation with the SDI (Spearman's r = 0.50, P < 0.001). Specificities of individual LDIQ items were >80%, except for neuropathy. Sensitivities were variable and lowest for damage, with <1% prevalence. Agreement between the SDI and LDIQ was >85% for all but neuropathy, reduced renal function, deforming arthritis, and alopecia. In the NDB, the LDIQ correlated well with the comorbidity index (r = 0.45), the Short Form 36 physical component scale (r = 0.43), the Medical Research Council dyspnea scale (r = 0.40), disability (r = 0.37), and the Systemic Lupus Erythematosus Activity Questionnaire score (r = 0.37).


CONCLUSIONS
The metric properties of the LDIQ are good compared with the SDI. It has construct validity and correlations with health assessments similar to the SDI. The LDIQ should allow expansion of SLE research. Its ultimate value will be determined in longitudinal studies.
Costenbader
Karen H
KH
Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
Khamashta
Munther
M
Ruiz-Garcia
Silvia
S
Perez-Rodriguez
Maria Teresa
MT
Petri
Michelle
M
Elliott
Jennifer
J
Manzi
Susan
S
Karlson
Elizabeth W
EW
Turner-Stokes
Tabitha
T
Bermas
Bonnie
B
Coblyn
Jonathan
J
Massarotti
Elena
E
Schur
Peter
P
Fraser
Patricia
P
Navarro
Iris
I
Hanly
John G
JG
Shaver
Timothy S
TS
Katz
Robert S
RS
Chakravarty
Eliza
E
Fortin
Paul R
PR
Sanchez
Martha L
ML
Liu
Jigna
J
Michaud
Kaleb
K
Alarcón
Graciela S
GS
Wolfe
Frederick
F
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000150:complications / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires
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