Transsexualism in a European context The value of NIRT in assessing the utility of DSM-IV-TR diagnostic criteria: a multi-site study on Gender Identity Disorder

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Transsexualism in a European context The value
of NIRT in assessing the utility of DSM-IV-TR
diagnostic criteria a multi-site study on
Gender Identity Disorder

• Muirne Paap
• Baudewijntje Kreukels
• Peggy Cohen-Kettenis
• Hertha Richter-Appelt
• Griet De Cuypere
• Ira Haraldsen

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Warning!

• The topic is applied (N)IRT
• no formulae/equations!

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About me

• Currently taking PhD at the clinic for Gender
  Identity Disorder (GID) in Oslo, Rikshospitalet
• Studied psychology with a major in clinical
  psychology and minor in statistics

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Collaboration

• Our clinic has a research collaboration with the
  clinics in Amsterdam, Hamburg and Ghent
• Goal standardize diagnostics and gather
  questionnaire data

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Background

• IRT has been gaining ground in psychiatric
  research
• investigating properties of clinical diagnoses or
  instruments
• DIF analyses

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Aim of this study

• is to use the DSM-IV-TR criteria for the
  diagnosis Gender Identity Disorder (GID) as an
  example to illustrate how the utility and
  generality of different aspects of diagnostic
  criteria for any DSM diagnosis can be
  investigated, using Nonparametric Item Response
  Theory (NIRT).

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GID Diagnosis 4 criteria

• Strong and persistent cross-gender identification
  
• Persistent discomfort about one's assigned sex or
  a sense of inappropriateness in the gender-role
  of that sex
• The diagnosis is not made if the individual has a
  concurrent physical intersex condition
• Clinically significant distress or impairment in
  social, occupational, or other important areas of
  functioning

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Criterion A

• Criterion A
• Stated desire to be the other sex
• Frequent passing as the other sex
• Desire to live or be treated as other sex
• Conviction that he or she has the typical
  feelings of the other sex

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Criterion B

• Criterion B
• Preoccupation with getting rid of sex
  characteristics
• Belief to be born the wrong sex

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Scoring

• Criteria from DSM were scored 0 or 1 on
• severity
• duration
• onset
• persistance
• frequency
• Item subcriterion x aspect

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Screenshot of scoring sheet
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Sample

• N214 applicants (mean age 32.3, SD 12.2),
  seen between jan 07 march 09
• 42 were biological females ( mean age 28.4, SD
  10.4) and 58 were biological males (mean age
  35.11, SD 12.7).
• 82 were diagnosed with GID (mean age 32.8, SD
  12.2). FtMs 90, MtFs 77.

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Method

• Comparing the centers
• On item (symptom) level
• On scale level
• Done by using Nonparametric Item Response Theory
  (Mokken-scale analysis) to construct scales and
  examine items

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NIRT

• Two models
• Monotone Homogeneity Model (MHM)
• Double Monotonicity Model (DMM)

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Main research question current project

• Are there any differences between centers in the
  way the GID-criteria are used to reach a
  diagnosis?
• Are the symptoms (items) interpreted in the same
  way in the four centers?
• Is the ordering with respect to popularity
  comparable?

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NIRT

• Some advantages in a clinical setting
• Any functional form of the IRF is allowed, as
  long as it is monotonely nondecreasing ? higher
  chance of good model-data fit
• Can be used for relatively small data-sets

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Results international scale

• ? When all data was analyzed together, only 1
  scale emerged, combining criterion A B!

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Results per center

• For three of the four clinics, a one-scale
  sollution was found, similar to the international
  one
• In Amsterdam, a two-scale sollution was found
• ? however, this was not a two-scale sollution
  congruent with the A and B criteria in the
  DSM-IV-R!

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Results - Amsterdam

• Scale one onset and duration items (Amst
  1)
• Scale two severity and persistence items
  (Amst 2)
• ? Dutch clinicians might have a different
  conception of GID

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Results IIO in subgroups

• The rank-order of the items, according to their
  difficulty, was similar over the four centers
• With the exception of the persistence and
  severity of Conviction that he or she has the
  typical feelings of the other sex
• These were relatively difficult items in Gent.
  To the contrary, in Hamburg the items are
  relatively easy

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IRF persistence conviction typical feelings of
the other sex
1 Gent 2 Hamburg 3 Amsterdam 4Oslo
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Summary

• With exception of 1 item, all items were used in
  a similar fashion in the four clinics when
  reaching a diagnosis (rank-order)
• Criterion A B ended up in one scale in our
  analysis (international scale)
• For Amsterdam, a two-scale sollution was found ?
  international differences in diagnostic decisions?

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Implications

• GID we would suggest that the severity and
  duration of symptoms should be taken into account
  in the next version of the DSM
• Generally we urge more researchers to consider
  to use NIRT to scrutinize diagnostic criteria (as
  listed in the DSM)

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Current developments

• At the moment the DSM-V is under development and
  it is being considered to enhance the DSM by
  adding a dimensional adjunct to each of the
  traditional categorical diagnoses in the DSM
• ? IRT!
• Kraemer HC DSM categories and dimensions in
  clinical and research contexts. International
  Journal of Methods in Psychiatric Research 2007
  16 S8-S15

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Thank you!

• Thank you for your attention!
• Any questions?
• Email muirne.paap_at_gmail.com