Page 2 US patient 1 to J 00 SSD and J 02 Conversion Disorder (FNSD)
Johnson et al took the results of their primary paper instrument, the DIS-III-R somatization section, from CFS, multiple sclerosis and depressed groups plus controls, and interpreted them using four separate criteria sets, each representing “a different approach for judging SD symptoms as psychiatric or physical”. Set 1 was an interpretation with a heavy psychiatric bias, consisting of “recording the total number of 48 SD symptoms on the DIS, which were coded as psychiatric” and also scoring as psychiatric all the complaints that are sometimes classified as ‘functional somatic’, including CFS itself.
Set 2 interpreted CDC-defined CFS symptoms as ‘organic’, not psychiatric. Additionally, both Sets 1 and 2 were divided into respective “a” and “b” subsets based on whether Escobar’s six symptom (for women)/four symptom (for men) cutoff for ‘subsyndromal somatization’ was used (subgroup “a”) or whether the full 13 symptoms was required for ‘full’ SD diagnosis (subgroup “b”).
For Set 3, the most ‘pro-biomedical’, only potential SD symptoms that existed prior to illness onset (CFS or MS) were scored as psychiatric; everything post-onset that the patient felt were due to their physical disease were scored as physical, not psychiatric. Lastly, Set 4 “used strict DSM-III-R criteria to determine prevalence of SD. Thus, only individuals with onset of CFS before age 30 who had 13 or more SD symptoms” were considered to have SD, and CDC CFS symptoms were again coded as physical in origin.
Their results were extremely revealing. No patients were diagnosed with SD by Set 3, whereas nearly 100% of CFS patients received an SD diagnosis in Subset 1a – however, this dropped to 52% in set 1b. More interestingly, despite the scoring of CDC CFS criteria as physical in Set 2, there was a >70% SD diagnosis rate in Subset 2a, but only 12% in Subset 2b. The difference in the subsets shows the huge change resulting from reduced specificity of SD criteria. Also of interest is that only one CFS patient was diagnosed with SD by Set 4 criteria, i.e. strict DSM-III-R SD criteria combined with exceptions for CDC CFS criteria.
In other words, the study predicts that a clinician who recognized CFS as a legitimate somatic disease by the CDC definition and stuck to the DSM-III-R criteria for SD would have found only a single one of the 42 CFS patients’ results consistent with an SD diagnosis, whereas a clinician who used less specific SD criteria, even while recognizing the CDC CFS symptoms as physical, would have found 10% to more than 70% to have SD (depending on the number of symptoms he used as a cutoff). It should be noted that the authors repeated Set 4 with DSM-IV SD criteria without significantly different results.
Johnson et al concluded that “the homogeneity of a patient population is critical when trying to evaluate a controversial syndrome such as CFS. The present study used the most homogeneous group of CFS patients of any study to date. Even with this reduced variability, prevalence rates of SD ranged from 0 to 98% depending on whether CFS symptoms were coded as being due to a physical illness or not [...] Thus, the judgments made regarding whether a symptom is coded as physical or psychiatric dramatically affect prevalence rates of SD in CFS”.
They noted the relatively high rate of somatization diagnoses in this study in Set 2 and in other studies using similar criteria, explaining that “These relatively high rates of SD, even after removing CDC criteria CFS symptoms from the equation, indicate that CFS subjects report many non-CFS symptoms that are then coded as psychiatric by the individual collecting the information”.