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

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 PaapBaudewijntje KreukelsPeggy Cohen-KettenisHertha Richter-Appelt

Griet De CuypereIra Haraldsen

Warning!

The topic is applied (N)IRT…

…no formulae/equations!

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

Collaboration

Our clinic has a research collaboration with the clinics in Amsterdam, Hamburg and Ghent

Goal: standardize diagnostics and gather questionnaire data

Background

IRT has been gaining ground in psychiatric research

investigating properties of clinical diagnoses or instruments

DIF analyses

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).

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

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

Criterion B

Criterion B:

Preoccupation with getting rid of sex characteristics

Belief to be born the wrong sex

Scoring

Criteria from DSM were scored 0 or 1 on: severity duration onset persistance frequency

Item = subcriterion x aspect

Screenshot of scoring sheet

Sample

N=214 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%.

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

NIRT

Two models:

Monotone Homogeneity Model (MHM)

Double Monotonicity Model (DMM)

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?

NIRT

Some advantages in a clinical setting:

1. Any functional form of the IRF is allowed, as long as it is monotonely nondecreasing higher chance of good model-data fit

2. Can be used for relatively small data-sets

Results – ’international scale’

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

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!

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

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’

IRF persistence conviction typical feelings of the other sex

1= Gent

2= Hamburg

3= Amsterdam

4=Oslo

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?

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)

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

Thank you!

Thank you for your attention!

Any questions?

Email: muirne.paap@gmail.com