The BILAG-2004 systems tally--a novel way of representing the BILAG-2004 index scores longitudinally.
OBJECTIVE
This was an exploratory analysis to develop a new way of representing BILAG-2004 system scores longitudinally that would be clinically meaningful and easier to analyse in comparison with multiple categorical variables.


METHODS
Data from a multicentre longitudinal study of SLE patients (the BILAG-2004 index and therapy collected at every visit) were used. External responsiveness analysis of the index suggested the possibility of using counts of systems with specified transitions in scores as a basis to analyse the system scores. Exploratory analyses with multinomial logistic regression were used to examine the appropriateness of this new method of analysing BILAG-2004 system scores. Receiver operating characteristic (ROC) curve analysis was used to assess the performance of this approach.


RESULTS
There were 1414 observations from 347 patients. A novel method was devised based on counts of systems with defined transitions in score (BILAG-2004 systems tally, BST). It has six components (systems with major deterioration, systems with minor deterioration, systems with persistent significant activity, systems with major improvement, systems with minor improvement and systems with persistent minimal or no activity). This was further simplified (simplified BST, sBST) into three components (systems with active/worsening disease, systems with improving disease and systems with persistent minimal or no activity). Both versions had expected associations with change in therapy. ROC curve analyses demonstrated that both versions had similar good performance characteristics (areas under the curve >0.80) in predicting increase in therapy.


CONCLUSIONS
The BST and sBST provide alternative approaches to representing BILAG-2004 disease activity longitudinally. Further validation of their use is required.
Department of Rheumatology, Doncaster Royal Infirmary, Armthorpe Road, Doncaster DN2 5LT, UK.
Chee-Seng
CS
Yee
Caroline
C
Gordon
David A
DA
Isenberg
Bridget
B
Griffiths
Lee-Suan
LS
Teh
Ian N
IN
Bruce
Yasmeen
Y
Ahmad
Anisur
A
Rahman
Athiveeraramapandian
A
Prabu
Mohammed
M
Akil
Neil
N
McHugh
Christopher
C
Edwards
David
D
D'Cruz
Munther A
MA
Khamashta
Vernon T
VT
Farewell
D000293:Adolescent; D000328:Adult; D000368:Aged; D003626:Data Display; D018450:Disease Progression; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012720:Severity of Illness Index; D055815:Young Adult