The UK Government, Improving Access to Psychological Therapies (IAP) only uses psychometric test screening measures to assess clients, most commonly the PHQ9 ( a measure of the severity of depression) and GAD7 (a measure of the severity of generalised anxiety disorder), but other measures are advised for other disorders, such as the PCL-5 for PTSD. A study by Zimmerman and Matia (2001) [The Psychiatric Diagnostic Screening Questionnaire: development, reliability and validity. Comprehensive psychiatry, 42(3), 175–189. https://doi.org/10.1053/comp.2001.23126 ] showed that questionnaire measures that reflect DSM criteria have a roughly 90% sensitivity across major depressive disorder, PTSD, panic disorder, social phobia and GAD, i.e it correctly identifies 9 out of 10 of those who do have one of these disorders. But it identifies only about 60% (specificity) of those who do not have the disorder and for GAD only 50%. However many more people do not have a particular disorder than have one, leading to unnecessary treatment for many. The National Audit Office should take note of this and re-instate its’ investigation, where is the due diligence with regards to IAPT? £4billion has been given to IAPT!
In the Zimmerman and Mattia (2001) study 47.9% of the psychiatric outpatients had major depression. Assuming psychiatric outpatients are a reasonable approximation to the IAPT population, then in a sample of 100 patients approx. 50 would have depression and 50 would not. Of the 50 with depression, 45 would have been correctly identified and treated. However of the 50 who did not have depression only, 30 would have been correctly identified leaving 20 as false positives, candidates for inapropriate treatment. Thus roughly for every two depressed cases appropriately treated one would be inappropriately treated. For depression the appropriate/inappropriate ratio is 2/1 – pretty wasteful.
Generalised Anxiety Disorder
In the Zimmerman Mattia Study 17.5% pf the psychiatric outpatients had GAD. Thus in a sample of 100 patients approx. 18 would have GAD, of whom 16 would have been correctly identified and treated. But 82 would not have GAD but 50% of them would have been regarded as having GAD meaning that 41 would have been inappropiately treated. Thus for GAD the appropriate/inappropriate ratio is 16/41, so that for every one GAD client treated appropriately 2-3 others are treated inappropriately.
Post-traumatic Stress Disorder
In the Zimmerman and Mattia study 10.5% of the psychiatric outpatients had PTSD. Thus in a sample of 100 clients approx. 11 would have PTSD with 9 being correctly classified and treated. However 89 would not have PTSD of these 62% (55) were correctly classified, meaning that 34 were false positives. Thus the ratio of appropriately treated/ inappropriately treated is approximately 1/4 , for every one treated appropriately 4 are treated inappropriately.
IAPT’s Preposterous Claim On Recovery
Given the ubiquity of unnecessary treatment in IAPT, its’ claim of a 50% recovery rate [IAPT Manual (2019)] is preposterous. I found a 10% recovery rate Scott (2018) https://doi.org/10.1177%2F1359105318755264, which is much more likely if a body relies simply on a screening instrument.
The Need To Translate Research Methodology Into Routine Practice
Ehlers et al. Trials (2020) 21:355 https://doi.org/10.1186/s13063-020-4176-8 have used the PDSQ to screen for cases of PTSD in their study of therapist assisted treatment for the condition, but have followed the screen up by using a standardised semi-structured interview the SCID to then diagnose PTSD. In this study they have kept a screen in its place and not allowed it free rein as in IAPT. The IAPT Manual p25 states ‘To ensure that all relevant problems are identified, it is recommended that assessments include systematic screening for each of the conditions that IAPT treats. Standardised commercial screening questionnaire that cover the full range of problems and that can be completed by people before they attend an assessment can be considered ‘ and cites the PDSQ as an example. But sole use of any screening instrument is very wasteful.
Ehlers et al (2020) have sought to establish whether no more than 4 hours therapist time can make a real world difference to PTSD sufferers lives, a consummation devoutly to be wished, these authors could be well employed helping IAPT get its’ own house in order.
Dr Mike Scott