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Brief Communication

Detection of Depression in Acute Schizophrenia:Sensitivity and Specificity of 2 Standard Observer

Rating Scales

Matthias J Mller1, MD, Kay-Maria Mller2, Andreas Fellgiebel, MD3

Key Words: depression in schizophrenia, Calgary Depression Rating Scale, HamiltonDepression Rating Scale, severity gradation

Can J Psychiatry, Vol 51, No 6, May 2006 W 387

Objective: To compare the psychometric properties of the Calgary Depression Rating

Scale (CDRS) and the Hamilton Depression Rating Scale (HDRS) for severity assessment

of depression in acute schizophrenia.

Method: During clinical routine treatment, we investigated 119 inpatients with acute

schizophrenia, using the CDRS, the HDRS, and a global 4-point Depression Severity Scale(DEP-SEV). We compared CDRS and HDRS sum scores regarding their diagnostic

accuracy, with global severity of depression as the criterion. We estimated sensitivity and

specificity on the basis of receiver operating characteristic curves.

Results: According to global clinical ratings (DEP-SEV), 31% of patients had no

depression, 19% had mild, 31% had moderate, and 19% had severe depression. Sensitivity

was significantly higher (P< 0.05) for the CDRS than for the HDRS to assess mild (0.94

vs 0.76, cut-off 3 vs 10 points) or severe depression (1.00 vs 0.78, cut-off 11 vs 22 points);

specificity was comparably high ($ 0.88) for both scales.

Conclusion: Despite the fact that both scales were effective in separating mild, moderate,

and severe depression, significant advantages emerged for the CDRS to detect mild or

severe depression in schizophrenia.

(Can J Psychiatry 2006;51:387392)

Information on funding and support and author affiliations appears at the end of the article.

Clinical Implications

CDRS and HDRS scales are useful to grade depression severity in schizophrenia.

The CDRS showed higher sensitivity in detecting mild and severe depression.

Results can help clinicians to initiate psychosocial interventions and medication.

Limitations

All assessments of individual patients were carried out by the same rater.

No fully standardized assessment of global depression severity was used. Replication is required because sampling bias cannot be entirely ruled out and sample size was

restricted.


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Depressive signs and symptoms are highly prevalent

during all illness states of schizophrenia (1), and depres-

sion is often associated with a heightened risk for suicide,

relapse or exacerbation, and lowered quality of life (2).

After the advent of atypical antipsychotics, the optimism has

increased that depressive symptoms could also become a tar-

get like positive and negative symptoms for more successfultreatment of schizophrenia patients. Some data and recom-

mendations corroborate this view (3,4), whereas results from

several studies combining antidepressants and antipsychotics

are still equivocal (5). Despite the broad agreement among

psychiatrists that depression in schizophrenia is associated

with considerable clinical burden (6,7), there is no consensus

regarding the best treatment strategy or clear indication for

initiating specific treatment (8). Thus the sensitive and spe-

cific assessment of depressive symptoms in schizophrenia is

importantfor diagnostic, prognostic, and therapeutic reasons.

The most appropriate dimensional assessment instrument

today is the CDRS (911), but the HDRS (12), from which

some modified items are also included in the CDRS (13), is

still widely used.

A score above 6 pointson the CDRShas beenproposed tosep-

arate schizophrenia patients with depression from those with-

out depression (14); a further study has found optimal cut-off

values of at least 7 points as related to major depression and

CDRS scores of at least 4 points to detect minor depression in

schizophrenia patients (15). However, studies directly com-

paring the accuracy of the CDRS and the HDRS for separating

clinically graded mild, moderate, and severe depression in

schizophrenia are still lacking.

MethodsWe investigated inpatients with stabilized acute schizophre-

nia diagnosed according to DSM-IV criteria.All patients gave

their consent after the study procedure was fully explained.

The study was approved by the local ethics committee and is

in full accordance with the German law.

Five experienced psychiatrists used the following tests during

clinical routine: the semistructured, 9-item CDRS (911); the

17-item version of theHDRS (12); a global4-point DEP-SEV

(0 = no depression, 1 = mild, 2 = moderate, and 3 = severe

depression); the PANSS (16); the severity item of the

CGI (17); and other psychopathological scales not reported

here. All raters had participated in continuous rater training.

Intraclass correlation coefficients (5 raters and 20 schizophre-

nia patients) were $ 0.87 for CDRS, HDRS, and DEP-SEV

ratings, indicating high interrater reliability. We assessed

global severity of depression according to DSM-IV criteria of

a major depressive episode with the following modifications:

severity of depression was rated independently of psychotic

features, and the time frame was set to 1 week. Means, SDs,

and the correlation of depression scores are reported. We

applied ROCs to evaluate and compare the diagnostic accu-

racy of the CDRS and HDRS sum scores, using global sever-

ity ratings as categorical criterion. We estimated AUC and

standard errors, as well as sensitivity and specificity with cor-

responding 95%CIs (18), and statistically compared them

between CDRS and HDRS scores (19). Nonoverlapping

95%CIs were regarded as statistically significant (P< 0.05).

Results

We investigated 119 inpatients (38% women and 71% para-

noid subtype) with a mean age of 31.9 years, SD 10.7. Age at

onset of schizophrenia was 26.8 years, SD 7.6; the inpatient

treatment duration at the time of assessment was 19.3 days,SD 11.1. All patients were under neuroleptic treatment (72%

atypical), and 28% received an antidepressant (19% a mood

s t a b i li z e r , 1 1 % a n t i c h ol i n e r gi c d r u g s , a n d 5 5 %

benzodiazepines) at the time of assessment. Mean PANSS

total score was 77 points, SD 22; PANSS positive symptoms,

18 points, SD 8; and PANSS negative syndrome, 21 points,

SD 8. The CGI severity score was 4.0 points, SD 1.3. Mean

scores of depression assessment were as follows: CDRS 6.4,

SD 5.8; HDRS 14.8, SD 8.7; and DEP-SEV 1.4, SD 1.1

points. The global assessment of depression severity ratings

revealed that 31% of patients had no depression, 19% had

mild depression, 31% had moderate depression, and 19% had

severe depression. The distribution of CDRS and HDRS

scoresis shown in Figure1, together with severity gradations.

For the severity categories of depression (mild, moderate,and

severe), the means and 95%CIs of CDRS and HDRS are

shown in Figure 2.

Generally, nonoverlapping CIs were yielded for CDRS, but

not for HDRS, scores (only mild, compared with moderate,

scores).

W Can J Psychiatry, Vol 51, No 6, May 2006388

The Canadian Journal of PsychiatryBrief Communication

Abbreviations used in the article

AUC areas under the ROC curve

CDRS Calgary Depression Rating ScaleCGI Clinical Global Impression

CI confidence interval

DEP-SEV Depression Severity Scale

HDRS Hamilton Depression Rating Scale

NS not significant

PANSS Positive and Negative Syndrome Scale

ROC receiver operating characteristic

SD standard deviation


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Detection of Depression in Acute Schizophrenia: Sensitivity and Specificity of 2 Standard Observer Rating Scales

Can J Psychiatry, Vol 51, No 6, May 2006 W 389

Score

0 5 10 15 20 25 30 35

Cumulativeproportionofpa

tients

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

"none"

"mild"

"moderate"

"severe"

CDSS

HAMD

>3

>7

>11

>10

>15

>22

Score

0 5 10 15 20 25 30 350 5 10 15 20 25 30 35

Cumulativeproportionofpa

tients

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

"none"

"mild"

"moderate"

"severe"

CDSSCDSS

HAMDHAMD

>3

>7

>11

>10

>15

>22

n = 119

The classification none, mild, moderate, severe is based on the DEP-SEV.

Figure 1 Cumulative distribution of CDRS and HDRS scores

Means (error bars: 95% CI for mean)30

25

20

15

10

5

0CDSS HAMD

no depression

mild depressionmoderate depression

severe depression

Means (error bars: 95% CI for mean)30

25

20

15

10

5

30

25

20

15

10

5

0CDSS HAMD

no depression


severe depression

no depression


severe depression

no depressionno depression

mild depressionmild depressionmoderate depressionmoderate depression

severe depressionsevere depression

Figure 2 Means of CDRS and HDRS scores

n = 119

CDSSHDRS

CDSS HDRS


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W Can J Psychiatry, Vol 51, No 6, May 2006390

The Canadian Journal of PsychiatryBrief Communication

0 20 40 60 80 100100-Specificity

100

80

60

40

20

0

Sensitivity

CDSS

HAMD

0 20 40 60 80 100100-Specificity

100

80

60

40

20

0

100

80

60

40

20

0

Sensitivity

CDSS

HAMD

CDSSCDSS

HAMDHAMD

Figure 3 Prediction of mild depression in schizophrenia by CDRS andHDRS scores

n = 119

Table 1 Global severity gradation and prediction by CDRS and HDRS scores

Severity gradation

(proportion of patients)

CDRS HDRS Difference

Cut-off 3 10

DEP-SEV 1 AUC 0.96 (0.02)a 0.89 (0.03)a P= 0.003

At least mild depression sensitivity 0.94 (0.86 0.98)b

0.76 (0.65 0.85)b

P< 0.05

(69%) specificity 0.88 (0.73 0.96)b 0.93 (0.80 0.98)b ns

Cut-off 7 15

DEP-SEV 2 AUC 0.97 (0.02)a

0.98 (0.02)a ns

At least moderate depression sensitivity 0.88 (0.76 0.96)b 0.90 (0.79 0.97)b ns


Cut-off 11 22

DEP-SEV = 3 AUC 0.99 (0.02)a 0.93 (0.04)a ns

Severe depression sensitivity 1.0 (0.96 1.0)b 0.79 (0.54 0.94)b P < 0.05


aAUC (standard error)

b95%CI

n = 119

Cut-off points are based on ROC analyses.

CDSS

HDRS


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HDRS scores were significantly correlated withCDRSscores

(r= 0.78, P< 0.001), and both depression scales were signifi-

cantly associated with DEP-SEV scores (CDRS r= 0.80, P

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