Q&A: A Quick Quantitative C-Reactive Protein Assay-Based DAPSA in Patients With Psoriatic Arthritis

In patients withpsoriatic arthritis (PsA), a quick quantitative C-reactive protein (CRP) assay-based Disease Activity index for PSoriatic Arthritis (Q-DAPSA) showed an almost perfect agreement with the conventional DAPSA regarding identical disease activity categories. This is according to a study published in the RMD Open.¹

Fabian Proft, MD

In this prospective multicenter cross-sectional study, researchers evaluated the DAPSA based on Q-DAPSA in 104 patients with PsA. Patient assessment included joint examination and patient reported outcome measures (patient global assessment, patient pain assessment). DAPSA was calculated based on a routine laboratory CRP measurement, after which Q-DAPSA and clinical DAPSA were calculated. With Q-DAPSA, 98.1% of patients achieved identical disease activity categories in comparison to DAPSA with a weighted Cohen’s kappa of 0.980 (95% CI: 0.952 to 1.000). With clinical DAPSA,the agreement with DAPSA was slightly lower at 93.3% and with a weighted Cohen’s kappa of 0.932 (95% CI 0.885 to 0.980).

In this Q&A, corresponding author Fabian Proft, MD, a rheumatologist and researcher at Charité Universitätsmedizin Berlin, discussed the research and its findings.

Rheumatology Network: Why was the study conducted?

Fabian Proft, MD: The DAPSA is one of the preferred tools for disease activity assessment in patients with PsA as a part of a treat-to-target (T2T) concept, but to calculate it you need a lab test for the acute phase reactant CRP. This takes hours or even days (in multicenter trials), which really complicates the use of DAPSA for prompt treatment decisions. Therefore, we wanted to investigate the use of the Q-DAPSA, based on a point of care CRP device that provides a solid CRP result after 2 minutes and only needs 1 drop of capillary blood (which can be collected from the fingertip or earlobe).

RN: What were the surprises from the findings?

FP: There were no surprises in the findings. The results provide the validation of the use of Q-DAPSA for disease activity assessment in patients with PsA. They also validate the use of Q-DAPSA for T2T treatment decisions in these patients.

RN: How significant are the findings?

FP: The Q-DAPSA showed an almost perfect agreement (>98%) with the conventional DAPSA regarding identical disease activity categories. Due to its immediate availability with the inclusion of an acute phase parameter (CRP), the Q-DAPSA can be used for regular disease activity monitoring and may ease the application of a T2T concept in patients with PsA.

RN: What is the current practice and how could the findings possibly change things?

FP: Currently, the patients need to come a couple of days before the visit to have their blood drawn and CRP analyzed so that the T2T decision based on the DAPSA can be done on the visit, or the last CRP value is used or the DAPSA is calculated when the patient has already left the clinic/hospital.

With the implementation of the Q-DAPSA, this can be overcome (and when it is only for disease activity assessment no whole blood draw is necessary but only 1 drop of capillary blood. This will facilitate the use of the DAPSA for disease activity assessment in clinical routine but also clinical T2T trials).

RN: What are the takeaway points for clinicians?

FP: Q-DAPSA shows an almost perfect agreement with the established DAPSA. Q-DAPSA has an immense time advantage of providing a result after 2 minutes and, with the possible use of capillary blood, is patient friendly.

Reference:

Proft F, Schally J, Brandt HC, et al. Evaluation of the Disease Activity index for PSoriatic Arthritis (DAPSA) with a quick quantitative C reactive protein assay (Q-DAPSA) in patients with psoriatic arthritis: a prospective multicentre cross-sectional study. RMD Open 2022;8:e002626. doi: 10.1136/rmdopen-2022-002626