Early CRPS Is a Heterogeneous Condition: Results From a Latent Class Analysis.

Background: Complex regional pain syndrome (CRPS) is a debilitating condition characterised by significant heterogeneity. Early diagnosis is critical, but limited data exists on the condition's early stages. This study aimed to characterise (very) early CRPS patients and explore potential subgroups to enhance understanding of its mechanisms.

Methods: A total of 113 early CRPS patients were recruited, with 89 undergoing physical assessments. Data included demographic information, work-related factors, CRPS history and clinical features, body perception disturbances, quantitative sensory testing (QST), and a visuospatial attention task.

Results: QST identified deficits in detecting thermal and mechanical stimuli, alongside increased sensitivity to thermal and blunt pressure painful stimuli. Participants reported body perception disturbances similar to those of persistent CRPS. Visuospatial biases were observed in two subgroups of patients. Latent class analysis (LCA) of 85 participants, based on five clinical parameters, identified four profiles: Mild, Moderate, Body Representation Disturbance (BRD), and Pressure Allodynia CRPS. The Mild and Moderate profiles were associated with higher-intensity trauma, with the latter showing worse outcomes. BRD and Pressure Allodynia CRPS followed mild trauma but exhibited the poorest outcomes. BRD CRPS displayed significant body perception disturbances, while Pressure Allodynia CRPS presented the highest sensitivity to pressure and psychosocial risk of chronification. Neither condition duration nor skin temperature effectively distinguished subgroups.

Conclusions: These findings emphasise the heterogeneity within (very) early CRPS patients and support the absence of a minimum required duration prior to the CRPS diagnosis. Central/systemic mechanisms may play critical roles in severe cases.

Significance: This study identifies distinct (very) early CRPS profiles, suggesting different pathophysiological mechanisms and challenging traditional classifications. It paves the way for improved diagnosis and tailored treatments.