Despite recent attention focused on CMC in the clinical setting, there are considerable inconsistencies in the way these children are defined in the research literature. Clinical and research initiatives would benefit from the use of a uniform definition that is clear, reproducible, and comparable across studies. This definition should be able to consistently identify children whose health and quality of life depend on integrating health care between a primary care medical home, tertiary care services, and other important loci of care such as transitional care facilities, rehabilitation units, the home, the school, and other community-based settings. The threshold for definition of CMC may be context-specific; definitions used in epidemiologic studies may differ from enrollment criteria for inclusion in clinical programs in different locales depending on resource availability, alternative models of care, and the specific family situation. Additional issues to address in operationalizing a definition for CMC include the periodicity of assessments, because complexity of care needs may change over time, as well as the mechanism to identify such patients (eg, individual providers, systems of care, parental reports, etc).
Our definitional framework adapts recommendations from a recent systematic review of chronic disease of childhood ().25
In this review, we propose a framework of 4 broad domains to characterize chronic conditions of childhood: needs; chronic conditions; functional limitations; and health care use. Conceptually, the combination of specific manifestations of each of these 4 domains encompasses the collective features of CMC.
FIGURE 1 Definitional framework for CMC among other definitions of chronic conditions of childhood.25 In this framework, CMC are defined as children with characteristic patterns of needs, chronic conditions, functional limitations, and health care use. CCCs are (more ...)
- Needs: CMC are characterized by substantial family-identified health care service needs such as medical care, specialized therapy, and educational needs. The service needs have a significant impact on the family unit, specifically time devoted to direct care, frequent provider visits, care coordination, and financial burden. The type, intensity, and consistency of these manifestations may change dynamically over the life of the child depending on a variety of medical, psychosocial, and community factors.
- Chronic condition(s): CMC have 1 or more chronic clinical condition(s), either diagnosed or unknown, that are severe and/or associated with medical fragility (eg, high morbidity and mortality rates). The condition and/or its sequelae should be expected to be potentially lifelong, although some children may improve with optimal care or with time. Examples may include a known condition identified among an established list of CCCs.26 An unknown but suspected complex and chronic condition, such as a child born with multiple congenital anomalies but lacking a unifying diagnosis, would be included.
- Functional limitations: Functioning is typically classified by using key dimensions of body structure and function, performance of activities, and participation in communal life.27,28 For CMC, the limitations are typically severe and may require assistance from technology such as a tracheostomy tube, feeding tube, or a wheelchair. The type, consistency, and severity of functional limitations may vary over the life of the child in the context of environmental and personal factors.
- Health care use: CMC typically have high projected utilization of health resources that may include frequent or prolonged hospitalization, multiple surgeries, or the ongoing involvement of multiple subspecialty services and providers. The intensity of health care use may also vary over time but is anticipated to be substantial when compared with other populations of CSHCN.
Clinical examples of CMC are described in the Appendix.
Our 4 domains complement the existing literature on CMC. Previous definitions lacked at least 1 domain, in part because of the data source or a particular focus such as family-identified needs, diagnostic and procedural codes, functional limitations, and resource use.
The National Survey of Children With Special Health Care Needs (NS-CSHCN) assesses family-reported need and enables state-level prevalence estimates and descriptions of CSHCN.29
One report described rising complexity by an increasing number of affirmative answers to 5 screening questions that identify special needs; there was a resultant upward trend in costs and service needs.3
The NS-CSHCN inquires about 16 common health conditions, the presence of 14 different functional limitations, and the use of numerous specific types of health services that may capture CMC. Although the condition list may detect many of the comorbidities among CSHCN, the NS-CSHCN lacks information about less common primary medical conditions that may be important contributors to the child's complexity, the duration, frequency, and severity of underlying chronic health issues, and specific details on functional limitations (such as technology dependence) and intensive service use, which may better capture and describe this key population.
In 2000, Feudtner et al26
compiled a list of International Classification of Diseases, Ninth Revision
–coded “complex chronic conditions” (CCCs) based on an operational definition of a medical condition that lasts for >12 months and involves several different organ systems or 1 organ system requiring a high level of specialty care and hospitalization. Examples of CCCs include brain and spinal cord malformations, metabolic disorders, cardiac and respiratory malformations, and malignancies. CCCs account for 2.3% of all newborn discharges from hospitals in Ontario, Canada,30
as well as an increasing proportion of childhood deaths26
and pediatric hospital care.31
There are limitations to approaches that rely exclusively on diagnostic codes. CCCs were not designed to describe the interaction of the condition with needs, functional limitations, and health care use. Thus, a particular CCC (eg, cystic fibrosis) can include children ranging from those who are virtually asymptomatic, and therefore unlikely to meet criteria to be considered CMC, to those with severe functional impairment who spend large portions of their lives interfacing with the health care system and would fulfill criteria for CMC. CCCs may also exclude children whose condition(s) is not defined by a particular coded diagnosis.
Other definitions of complexity focus on descriptions of functional domains and fragility in keeping with the World Health Organization's framework for classifying impairments, disabilities, and handicaps. These definitions include terms such as (1) children with multiple impairments (those with “significant physical disabilities combined with sensory and/or cognitive deficits”),1
(2) the technology-dependent child (“a child who requires both a medical device to compensate for the loss of a vital body function and significant and sustained care to avert death or further disability”),32
(3) the medically fragile child (who is either technology dependent or “requires substantial ongoing nursing care to avert death or further disability”),33
and (4) children with complex needs (“children with multiple health/developmental needs that require multiple services from multiple sectors, in multiple locations”).33
Of these definitions, medical technology dependence on devices such as a tracheostomy or enteral feeding tube has been most frequently used but by itself may only identify a smaller subpopulation of CMC.34
Lastly, administrative data have been used to profile resource use by classifying people into a health-status group and a severity level. Neff et al35,36
identified medically extreme “catastrophic” patients as having chronic conditions that are expected to be lifelong and progressive and to require extensive services. Examples of catastrophic conditions included quadriplegia, cystic fibrosis, and spina bifida. This “catastrophic” category comprised only 0.4% of the children but was responsible for 11% of health care charges and 24% of all pediatric hospital charges. However, in a follow-up article, Neff et al37
noted that only half of “catastrophic” children in a given year were identified because of the varying utilization between different years.
In sum, although a variety of definitions exist that capture 1 or more of the domains of CMC, each has its limitations. A definitional framework that captures needs, chronic conditions, functional limitations, and health care use is necessary to accurately describe this population of children and to develop interventions to improve their outcomes.