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  • Print publication year: 1998
  • Online publication date: August 2016

6 - Technical procedures



This chapter deals with the technical problems that must be solved in order to present for analysis the range of decisions made during the course of a clinical appraisal. The topics covered include the measurement of clinical course, the attribution of cause, the rating of interference with social function, the handling of multiple sources of information, the use of optional checklists, appendices and modules and the problem of missing data.

The basic principles are set out in the following text. The computer application discussed in Chapter 11 will provide more immediate online guidance.

‘Periods’ and ‘episodes’

SCAN data are analysed on the basis of defined time periods within or across which episodes of disorder may occur. An Episode is a period of time throughout which clinically significant symptoms persist, with no symptom-free intervals lasting three months or more. It could last for a few days or for many years. SCAN provides two alternatives for rating time periods: a standard or routine option, and a free episode list. Dates are determined by clinical judgement. Each is described below.

The routine SCAN option

The routine option also provides a choice of two periods, one for the present state and one for previous episodes. Both periods can be rated in either PSE-10 or IGC.

In the current period only Present State (PS) can be rated.

For the previous period two options exist: Representative episode (RE) and Lifetime Before (LB). The current period is rated in the left-hand box; RE or LB is rated in the right-hand box for each item.

Present State (PS)

When SCAN is used to structure the interview for a current period, the Present State (PS) represents a clinically significant disorder present during the month before the date of examination (approximately the last four weeks). As was the case with PSE-9, the term ‘month’ should be understood as notional or approximate; it could be extended up to 6 weeks or so, depending on the interviewer's clinical judgement. The episode need not have begun during the month; this would depend in part on the sample. The onset of PS could be years earlier. Therefore PS either constitutes an episode with an onset within the previous month, or is part of a longer episode.