This chapter discusses the standardization of instruments and typologies in social work assessment and introduces, from a multidimensional perspective, a new standardized instrument evaluating the level of complexity associated with the social intervention process in a sample of chronic kidney disease (CKD) patients. The authors evaluated the matrix's metric properties by internal consistency and defined a rating index through the best cutoff points, using receiver operator curve and Youden Index. Matrix construction and validation used focus groups of experts in blinded classification of 100 CKD patients and indicator weighting. The matrix shows good internal consistency and reliability (Cronbach's alpha = .742). Cutoff points indicate three levels of complexity classification. The matrix is a good instrument to identify the complexity associated with the social intervention process in the area of Nephrology, and is a relevant contribution to the social information management of social workers, the health teams and the administration of health units.