Prognosis Scenario

You have been asked by a 25 year old male patient, who has recently recovered from a first psychotic episode, how likely he is to have further episodes of illness. He wants this information before deciding if he should take prophylactic antipsychotic medication.

There remains some uncertainty about the precise diagnosis. He does not meet criteria for DSM-IV criteria at this stage. You prefer to use these criteria because of the important negative aspects of a false positive diagnosis. Your current working diagnosis is therefore non-specific – a first episode non-affective functional psychosis.

You form the structured question “In a patient with first episode functional psychosis, what is the likelihood of remaining free from relapse in the long term?”

You search Evidence-Based Mental Health and find a 15 year follow-up study of a Dutch cohort of patients with non-affective functional psychoses. You track down the original article (Schizophrenia Bulletin 1998 Jan 24 75-85)

• Is this evidence about prognosis valid?
• Is this valid evidence about prognosis important?
• Can you apply this valid and important evidence about prognosis in caring for your patient?

Completed Prognosis Worksheet for Evidence-Based Mental Health

Citation

Wiersma, D, Nienhuis, FJ, Slooff, C.J. and Giel R. Natural course of schizophrenic disorders: a 15-year followup of a Dutch incidence cohort. Schizophr.Bull. 24 (1):75-85, 1998.

Are the results of this prognosis study valid?

Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?
Yes – all patients in a circumscribed geographical region were included after the onset of their first ever episode of illness.
Was patient follow-up sufficiently long and complete?
Yes- up to 15 years
Were objective outcome criteria applied in a “blind” fashion?
Standard instruments were used with clear definitions of relapse although it is not clear that the follow-up was performed blind to baseline information
If subgroups with different prognoses are identified, was there adjustment for important prognostic factors?
Looked at a number of possible predictors of first relapse.
Was there validation in an independent group (“test-set”) of patients?
No

Are the valid results of this prognosis study important?

How likely are the outcomes over time?
After 15 years, 15% of patients had experienced no further psychotic episodes
How precise are the prognostic estimates?
95% confidence interval – 7% to 22%
If you want to calculate a Confidence Interval around the measure of Prognosis
Clinical Measure Standard Error (SE) Typical calculation of CI
Proportion (as in the rate of some prognostic event, etc) where:
the number of patients = n
the proportion of these patients who experience the event = p
$$sqrt{frac{p times (1-p)}{n}}$$
where p is proportion and n is number of patients
If p = 12/82 = 0.15 (or 15%) and n=82
begin{align} SE &= sqrt{frac{0.15 times (1-0.15)}{82}}\\
&= 0.039 text{ (or 3.9%)} end{align}
95% CI is 15% ±1.96 x 3,9% or 7% to 22%

Can you apply this valid, important evidence about prognosis in caring for your patient?

Do these results apply to your patient?
Were the study patients similar to your own?
Yes
Will this evidence make a clinically important impact on your conclusions about what to offer or tell your patient?
Yes

Psychosis: 15% Likelihood of remaining relapse free at 15 years

Clinical Bottom Line

Patients with first episode non-affective functional psychosis have a 15% likelihood of remaining free from relapse over 15 years.

Citation

Wiersma, D, Nienhuis, FJ, Slooff, C.J. and Giel R. Natural course of schizophrenic disorders: a 15-year followup of a Dutch incidence cohort. Schizophr.Bull. 24 (1):75-85, 1998.

Clinical Question

In a patient with first episode functional psychosis, what is the likelihood of remaining free from relapse in the long term?

Search Terms

hand search Evidence-Based Mental Health

The Study

Long term follow up of first-contact cases of non-affective functional psychosis from a geographically defined region in the Netherlands. At 6 months, 63% had DSM-IIIR schizophrenia or schizophreniform disorder. Explicit criteria were used for determining relapse. Data collection was standardised although much was retrospective from casenotes and informants.

The Evidence

Outcome Time Measure Confidence Interval
Relapse-free following remission of first episode 1 year 57% Not calculable
2 years 45% Not calculable
5 years 70% Not calculable
15 years 15% 7 to 22%