Posted by: ayrshirehealth | October 15, 2012

To screen or not to screen?- that is the question. by @colin_r_martin

Complexity of screening

I had the pleasure a couple of years ago to write an editorial entitled ‘Carry on Screening’ (Martin and Redshaw, 2009) for the Journal of Reproductive and Infant Psychology.  The focus of the piece was on the complexities of screening for psychological distress in the perinatal period and in particular some of the issues associated with screening questionnaires in terms of which are the most appropriate tools to use, the accuracy of such tools and so forth. It occurred to me recently to reflect on this piece within the broader context of the outcome of such screening practice irrespective of the choice of tool, and considering the impact of screening on care and management.

The context for this was quite interesting and informed by a study Rick Allan and I conducted a few years ago (Allan and Martin, 2009) looking at how useful the Hospital Anxiety and Depression Scale (HADS; Zigmond and Snaith, 1983) might be in individuals with psychotic symptoms.

Caveats and concerns

The rationale for our study was that the original validation of the instrument indicated that it should only be used in patients without psychotic symptoms, indeed the focus being medical and surgical patients, yet we were aware of a number of instances where this tool was being used for screening for depression in individuals experiencing psychotic symptoms in England.

Our study indicated some concerns and caveats about using this instrument for screening in this group, however, one of the most interesting aspects raised is the question of how does an instrument come to be used in groups that it was not designed for?

Evidence – what evidence?

It might seem that the evidence that supports the use of a tool in one group may be considered enough evidence to warrant its use in another group for screening, however, this assumes an appraisal of the evidence in a particular group has occurred.  It could easily be the case that tools such as the HADS may be used in some circumstances without any consideration of the evidence to support its application.

It is hard to say exactly the reasons and perhaps it is a mixture of many, however the reality of applying a screening tool outside its validation parameters must surely represent an issue of concern for all practitioners and researchers in mental health settings.

For the practitioner, a concern might be a positive screen indicates a specific intervention stream, or further screening burden on the individual. It may also indicate, in the case of a negative screen, the absence of a requirement for a specific intervention.  Either way, if the instrument is not validated for use within a particular group, there is the possibility of increased error in screening accuracy, a very important point when an instrument is used for this purpose.

Impact of screening

Given that questionnaire-based screening tools will inevitably determine both the concept of interest, for example, depression positive/depression negative status plus error, a lack of validation of the tool in a particular group is likely to increase such inherent error.  This raises at least two important questions for all of us working within mental health.

  • Firstly, what are the implications of screening for significant psychological distress if we are unsure of the evidence to support the use of the screening tool within a particular context?
  • Secondly, are we to say that there is something fundamentally different in screening within a mental health context than there is in a physical health context in terms of screening measure accuracy and veracity?

Specifically, are we more comfortable with implicit error in a screening measure for depression than we are in implicit error in a cervical smear screening test?  If that was the case, does it tell us anything about the relative importance and perception of screening across different fields of patient care, oncology, psychiatry, renal disease etc?

@colin_r_martin is professor of mental health at the University of the West of Scotland

References

Allan, R., & Martin, C. R. (2009). Can the Hospital Anxiety and Depression Scale be used in patients with schizophrenia? Journal of Evaluation In Clinical Practice, 15(1), 134-141.

Martin, C. R., & Redshaw, M. (2009). Carry on screening. Journal of Reproductive & Infant Psychology, 27(4), 327-329.

Zigmond, A. S., & Snaith, R. P. (1983). The Hospital Anxiety and Depression Scale. Acta Psychiatrica Scandinavica, 67(6), 361-370. doi: 10.1111/j.1600-0447.1983.tb09716.x

Tomorrow: day 6 0f 7 sees docherty_e reflecting on his visit, as an SPSP Fellow, to Alaska

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Responses

  1. […] To screen or not to screen?- that is the question by Colin R Martin on the Ayrshire Health blog. […]

  2. […] To screen or not to screen?- that is the question by Colin R Martin […]


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