Despite improvements in medical technology, longer life expectancy and better objective measures of health, claims for sickness benefits are high in Sweden and other Western countries, especially among women [1
]. Musculoskeletal disorders and psychiatric problems are the most common causes of sickness absence, long-term work incapacity and retirement due to ill-health among both men and women. An increasing proportion of claims is due to conditions characterised by subjective complaints, often with little objective pathology or impairment [2
]. The aetiology of sick-listing absence is multifactorial, comprising both medical and non-medical components [3
], and the prevalence and duration of sickness absence cannot always be explained by medical reasons alone [4
In Sweden as well as in other Western countries, medical certificates issued by physicians constitute the basis for decisions regarding sickness benefits and vocational rehabilitation. The processes of sick-listing and rehabilitation involve different professional categories with different training and functions, and communication between them occurs mainly in writing, on special forms. The right to sick-leave cash benefits for the individual patient is in Sweden determined by the employer for the first two weeks of absence, and thereafter by a case officer at a governmental agency, the Social Insurance Administration (SIA). Non-employed patients are reimbursed by the SIA for the entire period. In both cases a physician has to state on a medical certificate that the patient cannot work because of a disease or an injury. On this form the physician has to indicate the patient's main medical ICD-10 diagnosis code.
A description of the patient's functional problems and capabilities is also a crucial part of the certificate, and this is done by means of free text. The physicians' certificates have been found to have a substantial impact on the decisions on sick-listing benefits made by the SIA officers [5
]. Earlier studies have found that physicians perceive sickness certification as problematic, and that sickness certificates are often of poor quality [7
]. Work ability assessment is one of the most problematic aspects reported by physicians [13
The International Statistical Classification of Diseases and Related Health Problems (ICD) is the standard diagnostic classification for epidemiological and health management purposes [14
]. All national and local statistics on sickness absence morbidity are based on the coded main diagnosis. Little is known about co-morbidity or health problems in a wider sense in sickness absence. Sick-listing statistics based on ICD-10 have shown that for both men and women the two most common diagnostic groups in Sweden are musculoskeletal and psychiatric problems [16
The International Classification of Functioning, Disability and Health (ICF) is a WHO classification intended to be a tool for health statistics and research, as well as for clinical use and health care planning. ICF provides a multi-dimensional model of health and health related domains [17
]. ICF consists of four components: 1) Body Functions (BF) and Body Structures (BS), 2) Activities and Participation, 3) Environmental Factors, and 4) Personal Factors (not yet developed). Each component has 5-9 domains of functioning (BF and BS) or environmental factors (i.e. chapters). A disability is an umbrella term for impairments (BF and BS), activity limitations and participation restrictions that consist of up to 20 categories, which are the coding level. For BF and BS ICF provides a system for classification of data at four levels of detail and a system of qualifiers that may be used to classify the degree of disability (i.e. no, mild, moderate, severe or complete). The ICF short version is limited to the second level [18
]. ICF is not based on the concepts of disease; it includes neither causes of disability nor prognostic evaluation. ICD-10 and ICF are complementary, and WHO encourages health professionals to use these two classifications together, even though they can be used separately. ICD-10 includes symptoms and health related problems in addition to diseases, so ICD-10 and ICF are partly overlapping.
There is a steady increase in the published research on clinical applications of ICF, not least the development of ICF-based assessment tools, and on theoretical issues since its introduction in 2001[19
Functional status has been found to be a better indicator of health care needs than diagnosis [20
]. However, knowledge about functional problems among sick-listed patients is scanty and ICF is yet not commonly used in health care statistics. A recent review article [21
] found more than one hundred articles between 2001 and 2008 with attempts to link health related text-based information to ICF. To our knowledge, only one previous study has mapped information in sickness certificates to ICF: A recent Swedish study [22
] found that sickness certificates seem to provide scarce information on functioning and that the descriptions mainly concerned body components.
The primary aim of this study was to test the feasibility and reliability of ICF for classifying and coding disabilities as reflected in sick-leave certificates. A secondary aim was to explore the distributions of health problems and disabilities (i.e. regarding body functions, body structures, activities and participation) that cause work incapacity among men and women.