RT Journal
A1 Feinstein AR
T1 MUlti-item "instruments" vs virginia apgar's principles of clinimetrics
JF Archives of Internal Medicine
JO Archives of Internal Medicine
YR 1999
FD January 25
VO 159
IS 2
SP 125
OP 128
DO 10.1001/archinte.159.2.125
UL http://dx.doi.org/10.1001/archinte.159.2.125
AB 
The object of Apgar's attention—the clinical condition of a newborn baby—was not something tangible, like the length of a leg, the color of a fingernail, or the noise of a heart murmur. A baby's condition is an intangible clinical concept or "construct," somewhat like anxiety or congestive heart failure, that is not directly observed as an individual entity, but that can be perceived, interpreted, and rated from a set of pertinent observed phenomena.