Psoriatic arthritis (PsA) is a chronic inflammatory disease that can affect the joints, spine, tendons, and skin. Monitoring disease activity is important because ongoing inflammation can lead to pain, disability, and permanent joint damage. However, commonly used blood tests, such as C-reactive protein (CRP), do not always reflect how active the disease is.
In this study, we examined whether the neutrophil-to-lymphocyte ratio (NLR), a simple measure calculated from a routine blood count, could help assess disease activity in people with PsA. We analyzed data from more than 1,600 patients who were followed over nearly 10 years in a large prospective cohort. We compared NLR levels with multiple measures of disease activity, including joint and skin involvement, pain, patient well-being, and imaging findings.
We found that higher NLR levels were consistently associated with more active disease, greater pain, worse patient-reported outcomes, and radiographic damage. Importantly, these associations were observed even in many patients whose CRP levels were normal, suggesting that NLR may detect inflammation that is missed by traditional blood tests.
Because NLR is inexpensive, widely available, and already included in routine blood tests, it may provide clinicians with additional information when evaluating patients with PsA. These findings suggest that NLR could become a practical tool to help monitor disease activity and identify patients who may be at greater risk of poor outcomes.