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We read with great interest the recent paper by Aranow et al1 about the impact of laboratory results on scoring of the Physician Global Assessment (PGA) of disease activity in systemic lupus erythematosus (SLE). PGA is an important tool for assessing disease activity, response to treatment (it is a component of the Systemic Lupus Erythematosus Responder Index (SRI)-4) and remission in SLE. Importantly, monitoring of SLE through PGA has been recommended in the recent European League against Rheumatism (EULAR) guidelines.2
In their paper,1 Aranow et al found very high inter-rater PGA reliability values (pre-lab PGA intraclass correlation coefficient (ICC) 0.98; post-lab PGA ICC 0.99) based on 50 clinical vignettes. In our recent systematic review of the psychometric properties of the PGA,3 we show that this instrument is valid and responsive for assessing disease activity in SLE, but has a high variability. In the paper by Aranow et al, the inter-rater reliability of PGA was assessed using the ICC with a two-way random-effect model based on mean scorings (ICC 2,k). This has the effect of artificially increasing reliability estimates compared with the use of single measurement models (ICC 2,1), which would also be interesting to present.
This further suggests a major need for both standardisation and training in the scoring of this increasingly used instrument, particularly among non-expert rheumatologists, as those may wish to follow the recent EULAR recommendations for SLE.2
Contributors All authors contributed to the data analysis and preparation of the letter.
Funding The study was funded through the training Bursary Programme 2019 of the SLEuro European Lupus Society (recipient of the bursary: EC).
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; internally peer reviewed.
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