The prevalence and identification of anxiety disorders in pregnancy: the diagnostic accuracy of the two item Generalized Anxiety Disorder scale (GAD-2)

Objective To estimate the population prevalence of
anxiety disorders during pregnancy and investigate the
diagnostic accuracy of the two-item Generalised Anxiety
Disorder scale (GAD-2) for a) GAD and b) any anxiety
disorder.
Design Cross-sectional survey using a stratified sampling
design. Sampling weights were used in the analysis to
adjust for the bias introduced by the stratified sampling.
Setting Inner-city maternity service, South London.
Participants 545 pregnant women were interviewed after
their first antenatal appointment; 528 provided answers on
the GAD-2 questions.
Main outcome measures Diagnosis generated by the
Structured Clinical Interview for Diagnostic and Statistical
Manual of Mental Disorders, 4th edition (SCID).
Results Population prevalence of anxiety disorders
was 17% (95% CI 12% to 21%): 5% (95% CI 3% to 6%)
for GAD, 4% (95% CI 2% to 6%) for social phobia, 8%
(95% CI 5% to 11%) for specific phobia and 2% (95%
CI 1% to 4%) for obsessive-compulsive disorder. Posttraumatic
stress disorder (PTSD) prevalence was unclear
due to higher levels of reluctance to respond to PTSD
interview questions but sensitivity analyses suggest
population prevalence maybe up to 4% (95% CI 2% to
6%). Weighted sensitivity of GAD-2 for GAD (cut-off ≥3)
was 69%, specificity 91%, positive predictive value 26%,
negative predictive value 98% and likelihood ratio 7.35.
For any anxiety disorder the weighted sensitivity was 26%,
specificity 91%, positive predictive value 36%, negative
predictive value 87% and likelihood ratio 2.92.
Conclusions Anxiety disorders are common but GAD-2
generates many false positives and may therefore be
unhelpful in maternity services.