Response times follow lognormal or gamma distribution in arthritis patients.
OBJECTIVE
This study evaluated the statistical distribution of time to treatment response in patients with rheumatic diseases.


METHODS
The study used a secondary data analysis design. Data from the trial of etanercept and methotrexate with radiographic patient outcomes were used to model the response times for etanercept (ETN), methotrexate (MTX), and combined ETN+MTX in patients with rheumatoid arthritis. The German etanercept registry was used to evaluate the response time distributions in patients with juvenile idiopathic arthritis.


RESULTS
For MTX, the lognormal distribution was considered to be the best model for the outcome American College of Rheumatology (ACR20), lognormal, generalized gamma, and log-logistic distributions for ACR50, and lognormal and generalized gamma for ACR70. For ETN, the lognormal model was best for ACR20, the generalized gamma for ACR50, and both lognormal and generalized gamma distributions for ACR70. For combined treatment, the best model was the log-logistic distribution for ACR20, generalized gamma for ACR50, and both lognormal and generalized gamma distributions for ACR70. For the German etanercept registry, the lognormal distribution was the best model for all three outcomes of pediatric ACR30, ACR50, and ACR70 without interval censoring.


CONCLUSIONS
Study designs might be more efficient if the response distributions are taken into consideration during planning.
Abrahamyan
Lusine
L
Child Health Evaluative Sciences program, The Hospital for Sick Children Research Institute, University of Toronto, Toronto, Ontario, Canada.
Beyene
Joseph
J
Feng
JingYuan
J
Chon
Yun
Y
Willan
Andrew R
AR
Schmeling
Heinrike
H
Horneff
Gerd
G
Keystone
Edward C
EC
Feldman
Brian M
BM
D000328:Adult; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001171:Arthritis, Juvenile / Q000000981:diagnostic imaging / Q000188:drug therapy*; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D000068800:Etanercept; D005858:Germany; D006801:Humans; D007074:Immunoglobulin G / Q000627:therapeutic use*; D008297:Male; D008727:Methotrexate / Q000627:therapeutic use*; D011859:Radiography; D018124:Receptors, Tumor Necrosis Factor / Q000627:therapeutic use*; D012042:Registries; D012074:Remission Induction; D013997:Time Factors; D016896:Treatment Outcome
D018501:Antirheumatic Agents; D007074:Immunoglobulin G; D018124:Receptors, Tumor Necrosis Factor; D000068800:Etanercept; D008727:Methotrexate