WHAT ARE SCREENING TOOLS?
A screening tool uses a list of questions to identify who may have a high risk or likelihood of a disease or condition. Public Health England describe screening like a sieve: most people pass through because they are at low risk. However, some people’s results show a higher risk or likelihood of the condition. But further tests are required to confirm/diagnose the actual presence of that condition.
The two most commonly-used screening tools for dissociative disorders are the DES (Dissociative Experiences Scale) and the SDQ-20 (Somatoform Dissociation Questionnaire). The DES mainly looks at psychological symptoms whereas the SDQ-20 focuses on physical symptoms or body experiences.
These screening tools do not provide a diagnosis, but a higher score indicates a greater likelihood of suffering from a dissociative disorder, which would warrant further investigation. A full diagnosis is usually given using the SCID-D clinical assessment tool, delivered face-to-face by a qualified clinician, or the DDIS (Dissociative Disorders Interview Schedule).
There are limitations of the DES and SDQ-20 screening tools because they are self-report tools. There can be false positives: someone who overestimates their symptoms. There can also be false negatives: someone who underestimates or denies their symptoms. This is particularly true when people have ‘amnesia for amnesia’.
THE DES (DISSOCIATIVE EXPERIENCES SCALE)
For each experience on the DES questionnaire you were asked to select what percentage of the time this happens to you. You could choose between 0% (never) and 100% (always). The questionnaire is scored by taking the mean percentage: if you add up the percentages you gave for each question and divide it by the number of questions, you get the average percentage you gave.
A score of more than 30 indicates significant dissociative symptoms. Studies show that 74% of those with DID scored 30 or more on the DES. Where people scored over 30 but did not have DID, 61% had PTSD or another dissociative disorder.
AVERAGE DES SCORES IN RESEARCH
General adult population 5.4
Anxiety disorders 7
Affective disorders 9.35
Eating disorders 15.8
Borderline personality disorder 19.2
Posttraumatic stress disorder 31
Dissociative disorder not otherwise specified (DDNOS) 36
Dissociative identity disorder (DID) 48
Carlson, E.B. & Putnam, F.W. (1993). An update on the Dissociative Experience Scale. Dissociation 6(1): 16-27.
DES FACTOR ANALYSIS
Pathological/clinically significant dissociation can be assessed by a subset of 8 questions (3, 5, 7, 8, 12, 13, 22 and 27) and is called the DES-Taxon. The scores for these questions more strongly relate to the presence of pathological dissociation and a dissociative disorder.
THE SDQ-20 (SOMATOFORM DISSOCIATION QUESTIONNAIRE)
As there is a correlation between somatoform dissociative symptoms and a dissociative disorder, scoring someone’s somatoform symptoms can indicate a likelihood of a dissociative disorder.
The questions look at positive symptoms (pain, seizures, heightened taste and touch sensations) and negative symptoms (lack of pain, sensation, feeling numb, immobility). You were asked for each question to say whether each statement applied to you not at all (1) through to extremely (5). If they did apply, you were asked if there was a known physical cause for this symptom. If there was we adjusted your score to 1 for that question.
The test is scored simply by adding up the number you gave for each question and can range from 20 to 100. Studies have consistently shown that a score of 30 or more is suggestive of a somatoform disorder, 40 or more is suggestive of a dissociative disorder, and a score of 50 or more is suggestive of dissociative identity disorder in particular. This table shows the mean scores found in key research studies.
|STUDY||Nijenhuis et al. 1996||Nijenhuis et al. 1998||Nijenhuis et al. 1999||Sar et al. 2000|
|Major depressive episode||N/A||N/A||N/A||28.7|
|Mixed non-dissociative psychiatric patients (mainly anxiety and depression)||23.5||N/A||22.9||N/A|
|Bipolar mood disorder||N/A||N/A||21.6||22.7|
More information about the scoring and interpretation of the SDQ-20 can be found here.