Limitations
There are three main limitations to this review. Firstly to include
sufficient studies we could not restrict the time period and the
selected studies ranged over forty years. However the methodology for
identifying DELC and CAD remained unchanged in that period and we
believe all included studies are relevant. Secondly, although studies
used fairly consistent definitions of DELC and CAD, there was some
variance especially in the length of the crease. Three studies also used
>70% stenosis of at least one major epicardial vessel to
define CAD when the majority used 50% but it is not possible to
determine the impact that had on their results. Studies also varied in
using unilateral or bilateral creases to define DELC, although it was
noted that including unilateral creases appeared to reduce the odds
ratio and therefore significant results were still considered valid.
Lastly some studies used non-cardiac patients as controls and it was
assumed that they had no coronary artery disease without undergoing
angiography. We recommend that, for consistency, further studies assess
bilateral DELC and use Shresta’s(24) definition of a
deep (>1mm) diagonal crease extending obliquely at least
two-thirds from the tragus towards the outer border of the ear. This
should be assessed by two examiners with the patient upright and
patients with ear piercings which could cause iatrogenic creases should
be excluded. Similarly CAD should be defined as >50%
stenosis of at least one major epicardial vessel on angiography for both
case and control groups.