Patient Classification System

Acute to Intensive Care© y ATIC Complex©

ATIC assumes registered nurses are autonomous professionals, that they do not perform tasks neither have to organize their work based on tasks, but using person-centered care models, and improvement outcome-oriented models. That is why ATIC proposes a validated system to estimate and evaluate nursing care intensity and a validated system to identify individual complexity. 

What does workload mean?

Workload is the time and effort needed to perform direct, indirect, and other care tasks. Workload is a concept derived from Taylorian managerial models and task-centered models.  There are multiple nursing workload measurements tools however, they have not been able to reflect care complexity and intensity since they focus the tasks, not considering the characteristics of the person receiving care and the context of nursing care provision.

What does care complexity mean?

Care complexity is a cluster concept for individual complexity, therapeutic complexity, procedural complexity and organizational complexity.

What does individual complexity mean?

Individual complexity refers to the specific factors, characteristics and attributes of each person, with potential to generate an increase on the difficulty of nursing care provision, and to modify, in an incremental way, required nursing care intensity. ATIC offers a system to identify and categorize care complexity individual factors, using assessment elements of the ATIC terminology.

Categorization of individual complexity is presented in two levels: complexity sources and complexity factors.

Complexity sources act as bundlers or clusters for complexity factors.

Complexity sources
Comorbidity and Complications
Other complexity sources

ATIC Care complexity individual factors and their association to health outcomes are described in multiples scientific publications.

What does Acuity mean?

Acuity is an abstract cluster based on the care needs of each person, to determine care intensity in terms of required nurse hours per patient day.

What does Nursing care intensity means?

It is the amount of registered nurse time required for direct and indirect nursing care provision to each person.

What do Hour balance and Nurse staffing coverage mean?

Hour balance is the difference between available RN hours per patient day and required RN hours per patient day ( aNHPPD – rNHPPD ).

Nurse staffing coverage is the percentage of required RN hours per patient day that are covered by the available RN hours per patient day.

What do available RN hours per patient day mean?

Available RN hours per patient day are the total hours offered for RN care provision to a patient in a day (24 hours). Available hours may be calculated converting the number of RN in X during 24 hours, divided by the number of patients they have to care for in X during 24 hours, where X is the setting (ward, unit, facility).

What do required RN hours per patient day mean?

Required RN hours per patient day are the number of RN hours a patient needs during one day (24 hours.

rNHPPD may be calculated using the Acute-To-Intensive Care (ATIC) patient classification system.

What is the ATIC patient classification system?

The Acute-To-Intensive Care (ATIC) patient classification system is a validated method to estimate and predict the required RN hours per patient day, based on the weight of the main diagnosis in the nursing care plan.  

Its predictive capacity is almost excellent, where the área under the curve (AUC) = 0.81

What does Main nursing diagnosis mean?

The main nursing diagnosis is the problem that a RN identifies, among the diagnoses included in the care plan, that generates the greatest need of care in terms of immediacy, severity, risk, intensity and/or complexity.

Some examples:

Intensity cluster Care: Weight range of the main nursing diagnosis rNHPPD Equivalent ratio (RN : patients)
901 - 1000
31 - 42
2 o > : 1
801 - 900
21 - 30
1.5 : 1
701 - 800
14 - 20
1 : 1
601 - 700
10 - 13
1 : 2
501 - 600
7 - 10
401 - 500
5 - 7
301 - 400
3 - 5
201 - 300
2 - 3
101 - 200
1 - 2
1 - 100
0.1 - 1
ATIC diagnosis Weight Intensity cluster rNHPPD Ratio
Post-ICU syndrome
1 : 1
Risk of multiorgan failure
1 : 2
1 : 2
Risk of cardiogenic shock
1 : 3
Risk of disuse syndrome
1 : 3
Risk of sepsis
1 : 4
Risk of delirium recurrence/progression
1 : 4
Risk of hypovolemia
1 : 6
Risk of neurological deterioration
1 : 6
Risk of pancreatitis
1 : 6
Risk of post-surgical infection
1 : 8

How is the main diagnosis weight obtained?

ATIC offers pre-calculated weights based on a formula that considers patient severity and risk of death.

What does the weight value indicate?

The weight value indicates required RN care intensity.

In the ATIC system, this value is translated to equivalent required RN hours per patient day. This patient calssification system also includes a categorization of RN care intensity levels that cluster ranges of weights.

What does intensity cluster mean?

The ATIC patient classification system contains 10 levels of care intensity levels, ranging 100 points each, from occasional care to gigaintensive care, as shown in the examples.


Adamuz J, González-Samartino M, Jiménez-Martínez E, Tapia-Pérez M, López-Jiménez MM, Rodríguez-Fernández H, Castro-Navarro T, Zuriguel-Pérez E, Carratala J, Juvé-Udina ME. Risk of acute deterioration and care complexity individual factors associated with health outcomes in hospitalised patients with COVID-19: a multicentre cohort study. BMJ Open. 2021 Feb 17;11(2):e041726. doi: 10.1136/bmjopen-2020-041726.

Juvé-Udina ME, Gonzalez-Samartino M, Planas-Canals, M, Rodriguez-Fernández H, Batuecas-Duelt, I, Tapia-Pérez M et al. Acuity, nurse staffing and workforce, missed care and patient outcomes. A cluster-unit-level descriptive comparison. Journal of Nursing Management 2020

Adamuz J, Juvé-Udina ME, Gonzalez-Samartino M, Jimenez-Martinez E, Tapia Perez M, Lopez-Jimenez MM, Romero-García M, Delgado-Hito P. Care complexity individual factors associated with adverse events and in-hospital mortality. Plos ONE 2020. pone.0236370

Juvé-Udina ME, Adamuz J, Lopez MM, Tapia M, Fabrellas N, Matud C, Gonzalez-Samartino M. Predicting patient acuity according to their main problem. Journal of Nursing Management 2019

Adamuz J, Gonzalez M, Jiménez E, Tapia M, López MM, Ruiz MJ, Rodriguez H, Delgado P, Juvé-Udina ME. Care complexity individual factors associated with hospital readmission: a retrospective cohort study. Journal of Nursing Scholarship 2018 DOI: 10.1111/jnu.12393

Juvé-Udina ME, Fabrellas N, Adamuz J, Cadenas S, González M, de la Cueva L, Delgado P. Surveillance nursing diagnoses, ongoing assessment and outcomes on in-patients who suffered a cardiorrespiratory arrest. Revista da Escola de Enfermagem de USP 2017 51; e 03286.

Juvé-Udina ME. Capacidad discriminante del diagnóstico enfermero principal con el uso de la Terminología ATIC: estimación ponderal preliminar. ENE de Enfermería 2017 11(3)

Juvé-Udina ME, Farrero-Muñoz S, Matud-Calvo C, Jiménez-Pérez H, Rodriguez-Gías, E, Martinez-Muñoz, M. et al. Intensidad de cuidados enfermeros: ¿cargas de trabajo o complejidad individual?  Metas de Enfermería. 2010; 13(8): 6-14.