OBJECTIVE: To compare several methods of missing data imputation for function (Health Assessment Questionnaire) and for disease activity (Disease Activity Score-28 and Clinical Disease Activity Index) in rheumatoid arthritis (RA) patients. METHODS: One thousand RA patients from observational cohort studies with complete data for function and disease activity at baseline, 6, 12 and 24 months were selected to conduct a simulation study. Values were deleted at random or following a predicted attrition bias. Three types of imputation were performed: (1) methods imputing forward in time (last observation carried forward; linear forward extrapolation); (2) methods considering data both forward and backward in time (nearest available observation-NAO; linear extrapolation; polynomial extrapolation); and (3) methods using multi-individual models (linear mixed effects cubic regression-LME3; multiple imputation by chained equation-MICE). The performance of each estimation method was assessed using the difference between the mean outcome value, the remission and low disease activity rates after imputation of the missing values and the true value. RESULTS: When imputing missing baseline values, all methods underestimated equally the true value, but LME3 and MICE correctly estimated remission and low disease activity rates. When imputing missing follow-up values at 6, 12, or 24 months, NAO provided the least biassed estimate of the mean disease activity and corresponding remission rate. These results were not affected by the presence of attrition bias. CONCLUSION: When imputing function and disease activity in large registers of active RA patients, researchers can consider the use of a simple method such as NAO for missing follow-up data, and the use of mixed-effects regression or multiple imputation for baseline data.

• Klíčová slova
• DAS28, disease activity, epidemiology, outcomes research, rheumatoid arthritis,
• MeSH
• algoritmy MeSH
• indukce remise MeSH
• interpretace statistických dat * MeSH
• kohortové studie MeSH
• lidé MeSH
• lineární modely MeSH
• následné studie MeSH
• počítačová simulace MeSH
• revmatoidní artritida epidemiologie   MeSH
• stupeň závažnosti nemoci MeSH
• výzkumný projekt statistika a číselné údaje   MeSH
• zkreslení výsledků (epidemiologie) MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• pozorovací studie MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

Some evidences suggest that obesity impairs the effectiveness of TNF inhibitors. We examined the impact of body mass index (BMI) on the clinical effectiveness of abatacept in rheumatoid arthritis (RA) patients. This is a pooled analysis of 10 prospective cohorts of RA patients. All patients with available BMI were included in this study. The primary endpoint was drug retention of abatacept in the different BMI categories. Multivariable Cox regression was used to estimate hazard ratios (HRs) for drug discontinuation. A secondary endpoint was EULAR/LUNDEX response rates at 6/12 months. Of the 2015 RA patients initiating therapy with IV abatacept, 380 (18.9%) were classified as obese. Obese patients had more functional disability, and were less often RF positive. The median abatacept retention time was 1.91 years for obese RA patients compared to 2.12 years for non-obese patients (p = 0.15). The risk of abatacept discontinuation was not significantly different for overweight (HR 1.03 (95% CI 0.89-1.19)), or for obese (HR 1.08 (95% CI 0.89-1.30)) compared to normal-weight patients. Rheumatoid factor positivity reduced the risk of abatacept discontinuation (HR 0.83 (95% CI 0.72-0.95)), while previous biologic therapy was positively associated with drug interruption (HRs increasing from 1.68 to 2.16 with the line of treatments). Obese and non-obese patients attained similar rates of EULAR/LUNDEX clinical response at 6/12 months. Drug retention and clinical response rates to abatacept do not seem to be decreased by obesity in RA patients.

• Klíčová slova
• Abatacept, Body mass index, Drug survival, Rheumatoid arthritis,
• MeSH
• abatacept aplikace a dávkování   škodlivé účinky   MeSH
• antirevmatika aplikace a dávkování   škodlivé účinky   MeSH
• dospělí MeSH
• index tělesné hmotnosti * MeSH
• indukce remise MeSH
• Kaplanův-Meierův odhad MeSH
• lidé středního věku MeSH
• lidé MeSH
• multivariační analýza MeSH
• proporcionální rizikové modely MeSH
• prospektivní studie MeSH
• registrace MeSH
• revmatoidní artritida farmakoterapie   MeSH
• revmatoidní faktor krev   MeSH
• senioři MeSH
• výsledek terapie MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• multicentrická studie MeSH
• Geografické názvy
• Evropa MeSH
• Názvy látek
• abatacept MeSH
• antirevmatika MeSH
• revmatoidní faktor MeSH

BACKGROUND: Response to disease modifying antirheumatic drugs (DMARDs) in rheumatoid arthritis (RA) is often heterogeneous. We aimed to identify types of disease activity trajectories following the initiation of a new biologic DMARD (bDMARD). METHODS: Pooled analysis of nine national registries of patients with diagnosis of RA, who initiated Abatacept and had at least two measures of disease activity (DAS28). We used growth mixture models to identify groups of patients with similar courses of treatment response, and examined these patients' characteristics and effectiveness outcomes. FINDINGS: We identified three types of treatment response trajectories: 'gradual responders' (GR; 3576 patients, 91·7%) had a baseline mean DAS28 of 4·1 and progressive improvement over time; 'rapid responders' (RR; 219 patients, 5·6%) had higher baseline DAS28 and rapid improvement in disease activity; 'inadequate responders' (IR; 103 patients, 2·6%) had high DAS28 at baseline (5·1) and progressive worsening in disease activity. They were similar in baseline characteristics. Drug discontinuation for ineffectiveness was shorter among inadequate responders (p=0.03), and EULAR good or moderate responses at 1year was much higher among 'rapid responders' (p<0.001). INTERPRETATION: Clinical information and baseline clinical characteristics do not allow a reliable prediction of which trajectory the patients will follow after bDMARD initiation.

• Klíčová slova
• Abatacept, DAS28, Disease activity, Drug retention, Longitudinal data, Response rate, Rheumatoid arthritis,
• MeSH
• antirevmatika terapeutické užití   MeSH
• biologické faktory terapeutické užití   MeSH
• biologické markery MeSH
• komorbidita MeSH
• lidé MeSH
• následné studie MeSH
• progrese nemoci MeSH
• revmatoidní artritida diagnóza   farmakoterapie   MeSH
• stupeň závažnosti nemoci MeSH
• výsledek terapie MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• multicentrická studie MeSH
• Názvy látek
• antirevmatika MeSH
• biologické faktory MeSH
• biologické markery MeSH