Chapter 10. Mapping Disability Survey Questions to the ICF

10.1 Introduction

So far we have discussed the use of the ICF 1) as a conceptual framework and 2) as a classification system at the design stage. We now turn to the third application of the ICF in data collection - linking survey instruments to the ICF. The main purpose of mapping to the ICF is to aid comparison between disability surveys; at both national and international levels. In the first instance, this chapter will outline work currently being conducted at an international level on this mapping process. Following this we will (1) outline the methods employed in this process with regard to the coding of Body Functions, Activities and Participation and Environmental Factors (2) we will provide an example of how the pilot questionnaire could be mapped back to the ICF in the domains of ‘hearing’.

10.2 The DISTAB Project

In 1998, the UN Statistical Office completed the first international disability database called ‘DISTAT’. This database contains disability statistics from national household surveys, population censuses and administration records for 55 countries. Survey questions were back-coded to the ICIDH-1 to enable comparison. As highlighted by Mbogoni and Me, this comparison showed large variability in disability rates in part due to the question typology used among countries. According to Swanson et al (2003) DISTAT found similar yet distinct functioning concepts, such as hearing and listening mixed together in the same question. It has been recommended by DISTAT that a survey question needs to target a single level and type of functioning.

In 1999, a research group was set up - ‘DISTAB’ ultimately toproduce a set of survey items that could be used for data comparison internationally [1]. Part of this work involved the back coding of five national disability surveys. Back coding is defined in this instance as the process of matching the information about functioning obtained from a survey question to a code from the ICF. Seven topics were chosen from which to back-code questions – hearing, seeing, speaking, mobility (walking), body movement, gripping (with hands) or personal care.

Results

According to Swanson et al the ICF provides a well-defined structure for survey question comparison. A comparison of the back coded questions showed a large variability in the instruments used and highlighted the need for standardising surveys. Among the five questionnaires, questions were worded in ways that indicated different components of functioning (i.e. body structure and function, activity, participation and environment). Questions on seeing, for example, included both impairment and difficulty seeing, and activity level questions including seeing newspapers or faces. Swanson et al recommend that the format of the question as well as its focus be structured more clearly. Questions on behaviour can include many ideas in a single question and some (e.g. depression) can only be coded using the ICD – International Classification of Diseases.

10.3 ICF Coding Rules

The following are some important coding rules described in the ICF (WHO:21-23):

  • ICF uses an alphanumeric system in which the letters b, s, d and e are used to denote Body Functions (b), Body Structures (s), Activities and Participation (d), and Environmental Factors (e).
  • ICF categories are nested so that broader categories are defined to include more detailed categories as with this example of mobility under Activities and Participation:
d4Mobility(first-level item)
d410changing basic body position(second-level item)
d4105bending(third-level item)
  • Any individual may have a range of codes at each level which may be inter dependent or related.
  • The ICF codes are only complete with the presence of a qualifier, denoting a measurement of the difficulty, impairment. Qualifiers are coded as one, two or more numbers after a point or separator. At least one qualifier should accompany any codes else the codes will have no inherent meaning.
  • All three components classified in the ICF (Body Functions and Structures, Activities and Participation, and Environmental Factors) are all qualified using the same generic scale. Having a problem may mean an impairment, limitation, restriction or barrier depending on the construct. The scale is ranging from 0 to 4 to indicate severity and the use of 8,9 to indicate the reason for no severity code as shown below (the xxx denotes the 2 level 3 digit code):(WHO; 2002:22)
  • xxx.0 NO problem other terms (none, absent, negligible…)
  • xxx.1 MILD problem other terms (slight, low…)
  • xxx.2 MODERATE problem other terms (medium, fair…)
  • xxx.3 SEVERE problem other terms (high, extreme,…)
  • xxx.4 COMPLETE problem other terms (total…)
  • xxx.8 not specified
  • xxx.9 not applicable

The maximum number of codes per person can be 34 at the one digit level (8 body functions, 8 body structures, 9 performance and 9 capacity codes). At the two level the number of codes is 362. At more detailed levels these codes number up to 1424 items.

 As a person functioning can be affected at the body, individual and societal level the user should attempt to take into consideration all components of the classification; Body Functions and Structures, Activities and Participation and Environmental Factors.

 For survey data the ICF states that a set of 3 to 18 codes may be adequate to describe a case with two level 3 digit precision, with the more detailed four level version being used for specialist services (WHO,2001:23)

10.4 Implementation of ICF Codes

How a code is constituted is shown below using an example from the Activities and Participation component:

  • d denotes the component, in this case Activity & Participation
  • the first digit (4) denotes the chapter or domain, in this case mobility
  • the 2nd and 3rd digits (10) denote the second level category, in this case changing basic body position
  • the first digit after the decimal point (2) denotes the code for the performance qualifier, indicating in this case moderate difficulty with performance.

In summary therefore, if a case were coded as d410.28, from this we can tell that;

  1. The component being measured here is Activities and Participation – [(d) in chapter 4 - (d4)];
  2. The more specific activity being measured here is changing body position - (d410);
  3. The actual measurement used (through the survey or assessment) is firstly in terms of the person’s performance (what the person can do in their current environment) – the first qualifier tells us that this person experiences a moderate difficulty in performance – d410.2;
  4. The second qualifier which measures capacity (what a person can do a standardised environment was not measured (in the instrument used) as denoted by the 8 – d410.28.
  5. It is important to note that in using the A&P qualifiers, the performance code comes first after the decimal followed then by the capacity code.

The first and second qualifiers for the components of Body Functions, Activity & Participation and Environmental Factors are detailed in Table 34 below.

Table 34: Qualifiers for Body Functions, Activity & Participation and Environmental Factors

Components

First Qualifier

Second Qualifier

Body Functions (b)A generic qualifier (0 to 4; 8,9) indicating level of severity of impairment.
Example: b140.2 indicates a moderate impairment in the attention functions.
None
Activities & Participation (d)Performance Problem in person’s current environment.
Example: d5101.1_ indicates a mild difficulty with bathing the whole body with the use of assistive devices that are available to the person in his or her current environment.
Capacity Limitation without assistance
Example: d5101._2 indicates moderate difficulty with bathing the whole body implies that there is moderate difficulty without the use of assistive devices or personal help
Environmental Factors (e)Barriers/Facilitators
This is a generic qualifier with a negative and positive scale – to denote the extent of barriers and facilitators. Using a point alone denotes a barrier whereas using the + sign denotes a facilitator.
Example: e130.2 indicates that products for education are a moderate barrier. The code 130+2 would indicate that products for education are a moderate facilitator.
None

Source: WHO (2001:24)

10.5 Examples of Coding the NDA Pilot Questionnaire

There is much flexibility regarding how to assign codes in the domains of Activity & Participation and the Environmental Factors. (As noted earlier, the main questionnaires have the closest ICF codes - without the qualifiers - printed after the relevant items, as can be seen in Appendices 3 and 4). Some examples are provided here of ways in which different domains captured in the questionnaire can be coded.

Example of Coding - Activities and Participation Domain - Hearing Example

B2Do you have any difficulty hearing what is said in a conversation with one other person?

Response : No difficulty …………..Cannot hear

Using the ICF coding scheme this question would be coded under Activities and Participation, Chapter by using the (2 level 3 digit code - d310 ) - Communicating with receiving spoken messages.

A & P Qualifier

The question asks ‘do you have any difficulty’ therefore it is measuring ’performance’ denoted by the 1st qualifier (what a person can do in their current environment). Capacity is not measure in this question. The response scale used in the NDA survey and its mapping to the ICF qualifier can be seen in Table 35:

Table 35: Response Scale for NDA questions

NDA Response Scale

ICF Qualifier Code

No Difficultyd310.08
Just a little difficultyd310.18
A moderate level of difficultyd310.28
A lot of difficultyd310.38
You cannot heard310.48
Not specifiedd310.8
Not applicabled310.9

Environmental factors:

B8:Are there any aids, specialised equipment or services for persons who are deaf or hard of hearing that you think you need but do not have?

B9:Which aids or services do you NEED but do not have?

Hearing aid Yes/No

A computer to communicate Yes/No

A sign language interpreter Yes/No

If this same respondent answered ‘yes’ to B9 and ticked ‘hearing aid’ here the following code would apply:

e125.8 – this is because the person has indicated that they ‘need’ the particular aid or device therefore as there is an unfulfilled need – a barrier exists but the extent of the barrier isn’t specified.

  1. The countries involved in this mapping exercise were Canada (using HALS, 1991), France, Netherlands, South Africa and the US.