BOF: 2.41
In dual-energy x-ray absorptiometry (DXA), the T score
refers to:
a)
The number of standard deviations the patient’s bone mineral density
(BMD) is away from the mean values for BMD in a 30 year old of the same sex
and ethnicity.
b)
The number of standard deviations the patient’s bone mineral density
(BMD) is away from the mean values for BMD in age and sex matched controls
c)
The number of standard deviations the patient’s bone mineral density
(BMD) is away from the mean values for the general population
d)
The number of standard deviations the patient’s bone mineral density
(BMD) is away from the mean values for the local population
e)
The number of standard deviations the patient’s bone mineral density
(BMD) is away from the mean values for local age and sex matched controls
Answer
a)
Dual-energy x-ray absorptiometry provides accurate,
rapid, convenient assessment of bone mineral density (BMD)
The results are expressed as Z or T scores
The Z score refers to the number of standard deviations
the patient’s BMD values is away from age and sex matched controls
The T score refers to the number of standard deviations
the patient’s BMD is away from a young normal that is a 30 year old person of
the same sex and ethnicity as the patient.
At the age of 30 people have their peak bone mass.
WHO definition of osteoporosis
T >– 1.0 (Normal)
BMD equal to or more than 1 standard deviation (SD) below
the young adult mean
T –1.0 to –2.5 (Osteopaenia)
BMD 1.0to 2.5 SD below the young adult mean
T < 2.5 (Osteoporosis)
BMD more than 2.5 SD below the young adult mean
T <2.5 with one or more associated fractures
(Established /severe osteoporosis)
BMD more the 2.5 SD below the young adult mean with one
or more associated fractures
