diff --git a/pycen/sicen2/obs.py b/pycen/sicen2/obs.py
index 10163f8..d3230f6 100644
--- a/pycen/sicen2/obs.py
+++ b/pycen/sicen2/obs.py
@@ -145,22 +145,30 @@ def get_obs_serena(insicen:bool=None):
         .dropna(axis=1,how='all')
 
 
-
 def refresh_vm():
+    '''Rafraichissement de la vue materialisée vm_synthese_observations'''
     sql = "REFRESH MATERIALIZED VIEW saisie.vm_synthese_observations WITH DATA;"
     with con_sicen.begin() as cnx:
         cnx.execute(sql)
 
-def etude():
+
+def etude(with_data:bool=True):
+    '''Liste les études associées ou non à de la données'''
     from pandas import read_sql_query
-    sql = 'SELECT * FROM md.etude'
+    sql = 'SELECT e.* FROM md.etude e WHERE e.id_etude'
+    if with_data is True : sql += ' IN '
+    else : sql += ' NOT IN '
+
+    sql += '(SELECT id_etude FROM saisie.saisie_observation)'
     return read_sql_query(sql, con_sicen)
 
+
 def lot():
     from pandas import read_sql_query
     sql = 'SELECT * FROM md.lot'
     return read_sql_query(sql, con_sicen)
 
+
 def protocole():
     from pandas import read_sql_query
     sql = 'SELECT * FROM md.protocole'