Collaborative Care in the Treatment of Depressive Disorder Containing an Antidepressant Algorithm and PST; a Multicentre Cluster Randomized Trial in Primary Care

Reduction of depressive symptoms remission.

The severity of the symptoms is measured by the Inventory for Depressive

Symptomatology-Self Report (IDS-SR) and the Patient Health Questionnaire

depression subscale (PHQ9). The IDS-SR can be used for a global assessment of

depressive symptoms. The instrument consists of 30 questions on a *0-3 scale*.

The PHQ9 is a brief but valid instrument that scores each of the DSM-IV

criteria from *0* (not at all) to *3* (nearly every day).

Remission -reduction of DSM-IV criteria below threshold for a depressive

disorder diagnosis [ref APA]- is measured by the MINI interview at the end of

the intervention period (T1) and 12 months (T3), and with the PHQ9 -cut-off

score below 15-.

Cost utility, next to the improvement of severity of symptoms, the cost utility

of collaborative care compared to CAU is assessed in this design. Therefore, an

estimation of the direct medical costs and the costs due to production losses

(productivity costs) is made. Data for estimating the costs are collected by

using the Trimbos/iMTA questionnaire for Costs associated with Psychiatric

Illness (TiC-P). Quality of life is assessed by using the EQ-5D and the SF-36,

which are validated tools for measuring general health*related quality of life.



The cost utility is evaluated by relating the difference in direct medical

costs per patient receiving collaborative care or CAU to the difference in

terms of Quality Adjusted Life Years gained (QALY), which yields a cost per

QALY estimate. Furthermore, we also estimate the cost per QALY including the

productivity costs.





*Additional outcome measures and effectmodifcators:



1. Physical illness, as measured by the CBS-list, a questionnaire by the

Central Bureau of Statistics (CBS) in the Netherlands containing 28 chronic

conditions ranging from diabetes type II to Multiple Sclerosis.

2. Disability caused by the disorder, evaluated with the World Health

Organization Disability Assessment Survey II (WHO-DAS-II). WHO-DAS-II is

developed to assess the activity limitations and participation restrictions

actually experienced by an individual, irrespective of diagnosis. It has six

major domains: understanding and communicating with the world, moving and

getting around, self-care, getting along with people, life activities, and

participation in society. The instrument consists of 32 questions.

3. Adherence and compliance, assessed by the number of drop outs in the

intervention group compared to the CAU group.

Possible preferences of the patient, assessed by the choices of patients within

the intervention group.

4. Attitude of the GP towards the treatment of depressive disorder, measured

with the Depression Attitude Questionnaire (DAQ).

5. The patient-doctor working relationship, measuring this variable The Patient

Doctor Relationship Questionnaire (PDRQ-9) is included.

6. Treatment in the CAU group, assessed in patients and GPs with the Scale

Assessing Medical Utilization of Health Services.

7. Somatisation, the number and intensity of functional somatic complaints a

patient is experiencing is assessed with the LKV (Lichamelijke Klachten

Vragenlijst; Bodily Complaints Questionnaire). The LKV consists of 55

functional somatic complaints, ranging from headaches to fatigue on a scale

from *0 tot 3*.

8. Somatosensory amplification, the Whitely Index is the first questionnaire

specifically designed to assess hypochondriasis. It is also used for this

purpose in this study. The Whitely Index consists of 14 yes/no questions.

9. Life-events, to assess whether or not life-events can be seen as an

effectmodifier in this study, the Social Readjustment Rating Scale is also

included. The Social Readjustment Rating Scale consists of items that indicate

the amount of change in daily life; for example marriage scores 50 points on

the list. Taken together these items form the *Life change unit* that can be

used to quantify the stress of life-events, independently of the desirability

of those life-events.

10. Personality, is measured with the NEO-FFI. This is the short version of the

NEO, measuring the big five personality traits. It consists of 60 items on a

five point likert scale. There has been a debate whether or not the NEO remains

a valid instrument if someone is suffering from major depressive disorder, but

in a study by Duggan et al. (1995) current depressive symptoms did not explain

all the group differences in neuroticism after the effect of depression

(measured by the BDI) was partialled out. Therefore personality traits (to be

more specific neuroticism and introversion) are included in this study as

possible effectmodifiers.

11. Social support, will be assessed with the SOS (Social Support Scale, Dutch

version) This instrument consists of five items that measure the extent of

social support a patient receives.