Background/Purpose: The Physician Global Assessment (PGA) is a frequently-used outcome measure in Systemic Lupus Erythematosus (SLE). The PGA is intended to encapsulate the physician’s judgement of overall disease activity. Consensus on whether the PGA should be performed prior to, or after the receipt of laboratory values is lacking. A single-clinician pilot study in a US-outpatient clinic suggested that there are significant differences between the PGA score determined pre and post knowledge of labs¹. The primary objective of the current study was to determine, in a diverse international group of lupus experts, whether there is a difference in PGA scores with and without awareness of laboratory test results.

Methods: Fifty clinical vignettes based on real-life cases, spanning the spectrum of SLE manifestations and severity (SLEDAI-2K ranging from 0 to 28), were presented via an online survey to 194 international SLE experts. Respondents were asked to rate the PGA pre and post inclusion of laboratory test results for each case, with only forward progression through the survey allowed. Scoring of the PGA was done on an anchored scale of 0-3 with 0=none, 1=mild, 2=moderate and 3=the most active disease imaginable. Measures of central tendency and spread were used to describe responses, and Pearson’s correlation coefficient (CC) was used to evaluate the relationship between pre- and post-lab PGA for each case. Inter-rater reliability of PGA responses was assessed using the Intraclass Correlation Coefficient (ICC), and the correlation between PGA and SLEDAI-2K was also determined.

Results: There were 60 complete surveys (North America n=24, South America n=5, Europe n=15, Asia n=10, Australia n=6), comprising a data set of 3000 unique paired responses. The inter-rater reliability for PGAs was excellent (pre-lab ICC 0.98; post-lab ICC 0.99). Post-lab PGA were higher than pre-lab PGA: median (IQR) pre-lab PGA 0.5(1.05), post-lab PGA 1(1.3) (p<0.001), and the median (IQR) difference in post- and pre-lab PGA (delta-PGA) for all case pairs was 0.2(0.45). The correlation between pre and post-lab PGA was moderately strong (Pearson CC 0.79, 95% CI: 0.67-0.88, p<0.001). In 20 cases the CC was ≥0.8 and in 14 cases the CC was 0.6-0.79. In the 16 cases where the CC was ≤0.59, delta-PGA was median (IQR) 0.58 (0.68); these were mostly cases where lab data revealed lupus nephritis and/or hematologic manifestations. In general, all abnormal labs, including elevated anti-dsDNA and low complement level, impacted the PGA assessments. The correlation between SLEDAI-2K and PGA was higher for post-lab than pre-lab PGA (CC 0.79 and 0.67, respectively).

Conclusion: Although the PGA is known to be a subjective measure, we found excellent inter-rater reliability in a group of international lupus experts from six continents. Post-lab PGA scores had stronger correlation with SLEDAI-2K, and were generally higher than pre-lab PGA scores, with abnormalities on urinanalysis and cytopenias having the greatest impact. Overall, our findings indicate that the PGA should be performed with knowledge of the pertinent laboratory values.

¹ Aranow C. Immunol Res. 2015; 63(1-3):167-9.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/laboratory-investigation-results-influence-physicians-global-assessment-of-disease-activity-in-systemic-lupus-erythematosus/