Negative symptoms represent an unmet need of treatment in schizophrenia. Although
a consensus exists on negative symptom construct, and second generation assessment
instruments reflecting the consensus are available, studies still rely upon old assessment
instruments, that do not reflect recent conceptualizations and might limit progress
in the search for effective treatments. This is often the case in the European context,
where one of the challenges encountered in designing large studies is the availability
of validated instruments in the many languages of the continent. To address this challenge
and promote sound research on negative symptoms in Europe, the ECNP Schizophrenia
Network coordinated a large multicenter, multinational validation study of the Brief
Negative Symptom Scale (BNSS). Clinically-stable subjects with schizophrenia (SCZ,
N = 249) were recruited from 10 European Countries. Apart from BNSS, subjects were
administered the Positive and Negative Syndrome Scale (PANSS) and standardized instruments
for depression, extrapyramidal symptoms and psychosocial functioning. Results showed
an excellent internal consistency, convergent and discriminant validity of BNSS and
replicated a 5 factor-model. A larger number of subjects with predominant negative
symptoms, i.e. the target population for clinical trials, was identified by using
the BNSS compared to the PANSS. Regression analysis showed that BNSS-avolition, a
key negative symptom poorly assessed by PANSS, explained 23.9% of psychosocial functioning,
while no combination of the PANSS core negative symptoms showed the same impact on
functioning. The study demonstrated that BNSS has substantial advantages with respect
to PANSS for the identification of the avolition domain and subjects with predominant
negative symptoms.
