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In the US, the K10 is typically scored using a system where 0 is the minimum score for an answer (none of the time) and 4 is the maximum score (all of the time), with a possible total minimum score of 0 and maximum score of 40.
CATEGORISING K10 RESULTS (AUSTRALIA)
While no universally agreed categories or groupings exist for K10 scores, a number of different methods are used in Australia, depending on the purpose of administration and the setting in which it is delivered.
In ABS surveys, the score groupings and categories of psychological distress were developed drawing on an amalgam of the work of the Clinical Research Unit for Anxiety and Depression (CRUfAD), Andrews and Slade (2001), and Korten (submitted). Scores are grouped into four levels of psychological distress (see Table E, below).
Table E: ABS K10 score groupings and categorisation
Note: In the 1997 SMHWB, the scoring algorithm was reversed, so that low scores indicate high levels of psychological distress and high scores indicate low levels of psychological distress. Users of the 1997 SMHWB Confidentialised Unit Record File (CURF) need to recalculate scores to enable direct comparisons with other ABS surveys, as follows:
Low distress - 45-50 (normally 10-15)
Moderate distress - 39-44 (normally 16-21)
High distress - 31-38 (normally 22-29)
Very high distress - 10-30 (normally 30-50)
OTHER METHODS OF CATEGORISING
Table F, below, shows K10 score groupings and categories used by CRUfAD and GPcare in primary healthcare settings to assist in monitoring distress, rather than identifying the presence of a disorder (Coombs, 2011). This method was also used in the 2001 Victorian Population Health Survey.
Table F: CRUfAD & GPcare score groupings and categorisation
Table G shows K10 categories used by specialist mental health services for people who are already in specialist care. While the score groupings are identical to those used by CRUfAD and GPcare in Table F, the description for the corresponding level of psychological distress differs.
Table G: Specialist Mental Health Services score groupings and categorisation
There is also a ‘Plain English’ K10 categorisation, developed with AMHOCN and the Mental Health Association of NSW for interpreting K10 data in the 2002 Healthy Mind Day questionnaire. In this system, grouped scores are categorised into three levels of psychological distress, as shown in Table H, below.
Table H: ‘Plain English’ score groupings and categorisation
K6 SCORING & CATEGORISATION
The K6 is scored in the US using the same five-level response scale as the K10, where 0 is the minimum score for an answer (none of the time) and 4 is the maximum score (all of the time), with a minimum possible score of 0 and maximum possible score of 24.
Rules for optimal scoring of the K6 screening scale have been identified in Kessler et al (2003 & 2010), using ‘dichotomous’ (two groupings) and ‘polychotomous’ (multiple groupings) methods. As each scale item has five response categories and there are six items, the unweighted scale has values in the range 0-24 (US scoring) or 6-30 (Australian scoring). In most applications, based on standard validation studies, respondents with scores of 13-24 are classified as having a probable serious mental illness and those with scores of 0-12 as probably not having a serious mental illness (Kessler et al, 2010). Converted to Australian scoring, categories are as follows:
Table I: K6 Dichotomous score groupings and categorisation
The second method is a polychotomous scoring method where the K6 score groupings are refined into strata that differentiate between levels of serious mental illness (Kessler et al, 2010). Using Stratum-Specific Likelihood Ratio (SSLR) analysis, individual K6 scores are transformed into a score that represents the predicted probability of that person having a serious mental illness (Kessler et al, 2010; Furukuwa et al, 2003). Strata are shown using Australian scores in Table J, below.
Table J: K6 Polychotomous score groupings