Recommendations for optimizing the use of dysmorphic red blood cell counts in the clinical laboratory.

The assessment of dysmorphic red blood cells (RBCs) is of significant clinical interest in the evaluation of haematuria, particularly as a key tool for suggesting a possible glomerular origin. However, its actual utility depends on cautious, context-based interpretation supported by well-defined technical requirements. The lack of universal standardization, interobserver variability, and the influence of preanalytical factors continue to contribute to the heterogeneous implementation of this test in clinical practice. This document provides recommendations aimed at optimizing its use in the clinical laboratory. It reviews the underlying pathophysiological basis, principal indications, and the preanalytical and analytical conditions required to ensure reliable evaluation, as well as its integration with other findings from urinalysis and renal biochemistry. In this regard, erythrocyte dysmorphism should not be considered an isolated test, but rather a complementary parameter whose diagnostic performance improves when interpreted alongside proteinuria or albuminuria, renal function, the presence of pathological casts, and the patient's clinical context. Furthermore, the importance of a selective approach is emphasized, prioritizing clinical scenarios with higher diagnostic yield, such as persistent microhaematuria, haematuria associated with proteinuria, or suspected glomerular disease. Finally, guidance criteria are proposed for reporting and for integration into multidisciplinary clinical algorithms. Overall, these recommendations aim to promote a more rational, harmonized, and clinically meaningful use of dysmorphic RBC counts within advanced urinalysis.