Serial echocardiographic assessment of left ventricular mass: how blinded should readers be?
OBJECTIVE
In addition to the interest of mixing the sequence of echo-exam in a central blinded review, we studied the effect that might result from group-analysis of all echocardiograms simultaneously for each patient, with their sequence kept blind. A priori, this method of reading has the potential of decreasing measurement variability.


METHODS
We included 630 echocardiograms from 210 hypertensive patients participating in a randomized clinical trial comparing two antihypertensive agents for regression of left ventricular (LV) hypertrophy. Three echocardiograms per patient [selection (4 weeks before; W-4), at inclusion (week 0; W0), and the end of treatment (week 52; W52)], were read twice, according to two methods, blind to centre, patient numbers and sequence of visits: (1) examination of individual serial echocardiograms, (2) examination of all-patient mixed echocardiograms. The first method was expected to increase the power of treatment comparison by reducing variability of measurements of left ventricular mass (LVM).


RESULTS
Pooling echocardiograms of all patients reduces variability of LVM change under treatment: absolute LVM (W52 - W0) standard deviation was reduced by 22%. Nevertheless, despite a good between-methods agreement for LVM values at each visit (intra-class coefficient of correlation from 0.88 to 0.92), LVM change under treatment was reduced even more, by 41%. Thus, the slight decrease of variability induced by gathering the echocardiograms is associated with an even greater reduction of LVM change.


CONCLUSIONS
According to these findings, the 'full-blind' methodology for a central blinded review in clinical trials appears to produce the maximum power of the study with the lowest sample size.
Service de Cardiologie -- Hypertension Artérielle, Groupe Hospitalier Saint André, Bordeaux, France. philippe.gosse@chu-bordeaux.fr
Philippe
P
Gosse
Giovanni
G
de Simone
Olivier
O
Dubourg
Pascal
P
Guéret
Roland
R
Schmieder
D000959:Antihypertensive Agents / Q000627:therapeutic use; D004311:Double-Blind Method; D004452:Echocardiography / Q000592:standards* / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000000981:diagnostic imaging* / Q000188:drug therapy; D017379:Hypertrophy, Left Ventricular / Q000000981:diagnostic imaging* / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results
D000959:Antihypertensive Agents