Discordance in Diagnosis of Osteoporosis Using Spine
and Hip Bone Densitometry
A. El Maghraoui,* D. A. Mouinga Abayi, H. Rkain, and A. Mounach
Rheumatology and Physical Rehabilitation Department, Military Hospital Mohammed V, Rabat, Morocco
Diagnostic discordance for osteoporosis is the observation that the T-score of a patient varies between skeletal
sites, falling into 2 different diagnostic categories identified by the World Health Organization classification system.
Densitometrists and clinicians should expect that at least 4 of every 10 patients tested by dual-energy X-ray absorp-
tiometry (DXA) to demonstrate T-score discordance between spine and total hip measurement sites. T-score discor-
dance can occur for a variety of reasons related to physiologic and pathologic patient factors and the performance or
analysis of DXA itself.
Key Words: Bone mineral density; concordance; dual-energy X-ray absorptiometry; osteoporosis.
Osteoporosis is a metabolic bone disorder characterized by
low bone mass and microarchitectural deterioration, with
a subsequent increase in bone fragility and susceptibility to
fracture. Dual-energy X-ray absorptiometry (DXA) is recog-
nized as the reference method to measure bone mineral den-
sity (BMD) accurately and reproducibly. The World Health
Organization (WHO) has established DXA as the best densi-
tometric technique for assessing BMD in postmenopausal
women and based the definitions of osteopenia and osteopo-
rosis on its results (Table 1) (1,2). In clinical practice, BMD
measurements are widely used to diagnose osteoporosis and
to assess its severity, and changes in bone mass are commonly
used as a surrogate for fracture risk (3). The BMD values (in
g/cm2) are not used for diagnosing osteoporosis. Instead,
a working group of the WHO proposed to define osteoporosis
on the basis of the T-score (which is the difference between
the measured BMD and the mean value of young adults, ex-
pressed in standard deviations [SD] for a normative popula-
tion of the same ethnicity) (4,5). Despite its limitations, this
definition is currently applied worldwide. Thus, the WHO
diagnostic criteria for osteoporosis define osteoporosis in
terms of a T-score below ?2.5 and osteopenia when T-score
is between ?2.5 and ?1. These figures are usually calculated
separately for 2 different sites of lumbar spine and total hip.
Although the BMD at different anatomic regions is corre-
lated, the agreement between sites is low when it comes to
classifying individual subjects as osteoporotic or not (6).
Thus, T-score discordance between the lumbar spine and total
hip testing sites is a commonly observed phenomenon in den-
sitometry. T-score discordance is the observation that the T-
score of an individual patient varies from 1 key measurement
site to another. This phenomenon has been divided into 2
groups: major and minor (7). Minor discordance happens
when the different diagnostic classes are adjacent, that is, pa-
tient is diagnosed as osteoporotic in 1 site and osteopenic in
the other site, or, osteopenic in 1 site and normal in the other
site. If the diagnosis is osteoporosis in 1 site and the other site
is in the normal range, the discordance falls into the major
class. Actually, as the presence of discordance can affect
the diagnosis and therapeutic plan in an individual person,
it is highly recommended to measure BMD in several sites.
Prevalence and Risk Factors
of T-Score Discordance
Various studies have analyzed the prevalence and impact
of T-score discordance on the management of osteoporosis
Received 11/07/06; Revised 12/07/06; Accepted 12/08/06.
*Address correspondence to: Prof. A. El Maghraoui, MD, Rheu-
matology and Physical Rehabilitation Department, Military Hospital
Mohammed V,PO Box 1018,
Journal of Clinical Densitometry, vol. 10, no. 2, 153e156, 2007
? Copyright 2007 by The International Society for Clinical Densitometry
(7e12). Only 2 studies focused on risk factors of this com-
monly observed discordance (12,13). Table 2 shows the
results of data analysis of 3 major studies of T-score discor-
dance between spine and total hip measurement.
Nelson et al. (14) reported data on 537 patients who were
osteoporotic at 1 site and normal at another site. They found
a 3.5% prevalence of major discordance between the total hip
and the posteroanterior (PA) lumbar spine. Woodson’s data
analysis about 5627 patients (7) showed that using the
WHO diagnostic classification system, simultaneously mea-
sured T-scores at the PA L1eL4 total spine and total hip
are concordant in 56% of patients and discordant by at least
1 diagnostic class in 44%. Minor discordance, present when
the PA L1eL4 total spine and total hip sites differ by only
1 WHO diagnostic class, was found to be common, occurring
in 39% of patients. Major discordance, present when 1 site is
osteoporotic and the other is normal, was unusual, having
a prevalence of only 5%. The first study to look for potential
risk factors for T-score discordance enrolled 4188 persons
(12). Totally, 518 participants were diagnosed in osteoporotic
range in hip area and 1036 participants in the lumbar area.
Major discordance was observed in BMD results of 115
(2.7%) participants. Minor discordance was observed in
1631 (38.9%) participants and T-score categories of 2 mea-
surement sites in other 2442 (58.3%) participants were not
different. T-score discordance was more prevalent in women
than men (42.2% vs 36.5%, p5 0.042). The mean age of par-
ticipants with discordance (54.8 yr) was higher than the other
group (52.5 yr, p ! 0.001). In 3848 female participants, the
number of postmenopausal women with diagnostic discor-
dances (951 of 2027) was significantly higher than premeno-
pausal participants with discordance (671 of 1821; p!
0.001). In multivariate analysis, participants with late meno-
pause (age at menopause O50) were more likely to show
T-score discordances. Obesity defined as body mass index
(BMI) over 30 was recognized as a risk factor for major dis-
cordance and smoking as a protective factor against minor
discordance. Hormone replacement therapy was a significant
protector against both. To look for prevalence and risk factors
of T-score discordance in our center, we recently studied 3015
persons (13): 259 participants diagnosed in osteoporotic range
at the hip site and 792 participants at the PA L1eL4 total
spine. Major discordance was observed in BMD results of
129 (4.3%) participants. Minor discordance was observed in
1250 (41.5%) participants and T-score categories of 2 mea-
surement sites in other 1636 (54.3%) participants were con-
cordant. T-score discordance was equally observed in
women and men (44.1% vs 46.0%, p 50.42). The mean
age of participants with discordance (56.1 yr) was higher
than in the other group (52.6 yr, p! 0.0001). In 2486 female
participants, the number of postmenopausal women with
diagnostic discordances (915 of 1739) was significantly
higher than premenopausal participants with discordance
(231 of 747; p! 0.0001). In multivariate analysis, partici-
pants with menopause, obesity (defined as BMI over 30),
WHO Osteoporosis Classification
Distribution of Diagnostic Discordances Using WHO Criteria in 3 Studies
Moayyeri et al. (12)
et al. (13) (n5 3015)
Major T-score discordance
Hip osteoporosis, normal lumbar
Hip normal, lumbar osteoporosis
Minor T-score discordance
Hip osteoporosis, lumbar osteopenia
Hip osteopenia, lumbar osteoporosis
Hip osteopenia, normal lumbar
Hip normal, lumbar Osteopenia
Hip and lumbar osteoporosis
Hip and lumbar osteopenia
Hip and lumbar normal
Numbers are presented as frequency (percentage in parenthesis).
154El Maghraoui et al.
Journal of Clinical DensitometryVolume 10, 2007
and history of fractures were more likely to show major
T-Score Discordance Etiologies
Five different causes for occurrence of discordance
between the spine and the hip sites have been described (7).
1. Physiologic discordance is related to the skeleton’s natu-
ral adaptive reaction to normal external and internal fac-
tors and forces. Mechanical strain especially related to
weight bearing plays a key role in this kind of discor-
dance. An example of this type of discordance is the dif-
ference observed between the dominant and nondominant
total hip. The explanation is that weight bearing can cause
rise in bone density especially in the hip and femur
regions (15). This mechanism could be the reason of
more major T-score discordances observed by increment
of BMI as confirmed by the multivariate analysis in the
studies by Moayyeri et al. and El Maghraoui et al. More-
over, the spine and hips usually start out with different T-
scores (the spine is said to reach peak at least 5 yr before
the hip). And finally, bone loss observed with age in an
individual may be more rapid and important in trabecular
than cortical bone is another explanation. In both discor-
dances observed in our study, lower BMD for lumbar
spine was more prevalent. The main explanation was
that rates of bone loss differ substantially between the
anatomic regions in the same individual (16). Trabecular
bones (typical of lumbar area) are known to have a more
rapid rate of deprivation in early postmenopausal state in
comparison to cortical bone (typical of proximal femur).
Indeed, major T-score discordances were associated with
menopause in studies by both Moayyeri et al. and El
Maghraoui et al. (odds ratio 5 1.7; 95% confidence inter-
val [CI]: 1.01e2.7 and 6.04; 95% CI: 2.75e13.28, respec-
2. The second type of discordance described as pathophysi-
ological discordance and which can also be called sec-
ondary discordance is seen secondary to a disease or
medication use. Two subtypes of secondary discordance
can be observed. The first subtype is related to a disease
responsible of falsely elevated lumbar spine T-score.
Common examples observed in the elderly include verte-
bral osteophytosis, vertebral end plate and facet sclerosis,
osteochondrosis, and aortic calcification (17,18). Another
important cause in younger patients is ankylosing spondy-
litis syndesmophytes (19e21). The abnormal calcium
deposition within the field of the DXA region of interest
(ROI) leads to the falsely elevated spine T-score. The sec-
ond subtype is a secondary true discordance resulting
from a more decreased BMD in the lumbar spine than
the hips. Indeed, most of the etiologies of the secondary
osteoporosis (such as glucocorticoid excess, hyperthy-
roidism, malabsorption, liver disease, and rheumatoid
arthritis) first affect spinal column (20,21). This will
lead to higher prevalence of lumbar osteoporosis.
3. Anatomic discordance is owing to differences in the
composition of bone envelopes tested. An example is
the difference in T-scores found for the PA lumbar spine
and the supine lateral lumbar spine in the same patient.
4. Artifactual discordance occurs when dense synthetic
manmade substances are within the field of ROI of the
test (e.g., barium sulfate, metal from zipper, coin, clip,
or other metallic object).
5. And finally, technical discordance occurs because of
device errors, technician variability, patients’ movements,
and variation due to other unpredictable sources. With re-
spect to positioning error, some studies showed that either
excessive internal or external rotation of the femur during
test acquisition resulted in a BMD difference of as much
as 10% compared with correct positioning. This is equal
to a 1 SD difference or a full T-score, clearly enough to
cause discordance with the spine. We demonstrated in
a previous study that DXA in vivo reproducibility is 2-
fold better in the hips than in the spine especially when
measuring both hips (22). Technical discordance can also
result when the method used by the technician to analyze
shifting the BMD up or down. Although in the usual case
both the hip and spine would be shifted in the same direc-
tion, the result of such a shift might cause the apparent dis-
cordance. Finally, technical discordance can occur due to
the normative reference data used by the device software
to analyze the test. This type of discordance occurs when
the average BMD of the normative group used to calculate
the T-score issignificantly different fromthe averagevalue
found for the whole population.
Consequences of T-Score Discordance
on Osteoporosis Management
The high prevalence of T-score discordance could induce
some problems for the physicians in decision making regard-
ing these patients. In general, high prevalence of discordance
between lumbar spine and hip T-scores suggests some defects
in the cutoff values for definition of osteoporosis and osteope-
nia proposed by the WHO. The international societies inter-
ested in osteoporosis management recommend using DXA
to measure BMD in both the hip and spine and classifying
the patient based on the lowest T-score of these measure-
ments. The inconsistencies in the diagnostic classification of
osteoporosis between skeletal sites lend credence to the
notion that BMD should be used as only 1 of the factors in
making therapeutic decisions when evaluating patients with
osteoporosis. An international team convened by the WHO
is trying to develop a globally applicable measure of absolute
fracture risk based on multiple risk factors including BMD.
This could silence much of the controversy regarding choice
of reference data for T-score calculation and usefulness of rel-
atively arbitrary densitometric categorizations (14).
In summary, the densitometrists and clinicians should be
prepared to expect that at least 4 of every 10 patients tested
Diagnostic Discordance for Osteoporosis 155
Journal of Clinical Densitometry Volume 10, 2007
by DXA demonstrate either minor or major T-score discor- Download full-text
dance between spine and total hip measurement sites. T-score
discordance can occur for a variety of reasons related to phys-
iologic and pathologic patient factors and the performance or
analysis of DXA itself.
1. Consensus Development Conference. 1993 Diagnosis, prophy-
laxis and treatment of osteoporosis. Am J Med 94:646e650.
2. World Health Organization. 1994 Assessment of fracture risk
and its application to screening for postmenopausal osteoporo-
sis. In: Technical Report Series 843. WHO, Geneva.
3. El Maghraoui A, Guerboub AA, Achemlal L, et al. 2006 Bone
mineral density of the spine and femur in healthy Moroccan
women. J Clin Densitom 9(4):454e460.
4. El Maghraoui A, Guerboub AA, Achemlal L, et al. 2006 Nov 27
Body mass index and gynecological factors as determinants of
bone mass in healthy Moroccan postmenopausal women. Matur-
itas. [Epub ahead of print].
5. El Maghraoui A, Koumba BA, Jroundi I, Achemlal L, Bezza A,
Tazi MA. 2005 Epidemiology of hip fractures in 2002 in Rabat,
Morocco. Osteoporos Int 16(6):597e602.
6. Faulkner KG, von Stetten E, Miller P. 1999 Discordance in pa-
tient classification using T-scores. J Clin Densitom 2:343e350.
7. Woodson G. 2000 Dual X-ray absorptiometry T-score concor-
dance and discordance between the hip and spine measurement
sites. J Clin Densitom 3:319e324.
8. Mulder JE, Michaeli D, Flaster ER, Siris E. 2000 Comparison of
bone mineral density of the phalanges, lumbar spine, hip, and
forearm for the assessment of osteoporosis in postmenopausal
women. J Clin Densitom 3:373e381.
9. Abrahamsen B, Stilgren LS, Hermann AP, et al. 2001 Discor-
dance between changes in bone mineral density measured at dif-
ferent skeletal sites in perimenopausal womendimplications for
assessment of bone loss and response to therapy: the Danish Os-
teoporosis Prevention Study. J Bone Miner Res 16:1212e1219.
10. Hans D, Rizzoli R, Thiebaud D, et al. 2001 Reference data in
a Swiss population. Discordance in patient classification using
T-scores among calcaneum, spine, and femur. J Clin Densitom
11. O’Gradaigh D, Debiram I, Love S, Richards HK, Compston JE.
2003 A prospective study of discordance in diagnosis of
osteoporosis using spine and proximal femur bone densitometry.
Osteoporos Int 14:13e18.
12. Moayyeri A, Soltani A, Khaleghnejad Tabari N, Sadatsafavi M,
Hossein-Neghad A, Larijani B. 2005 Discordance in diagnosis
of osteoporosis using spine and hip bone densitometry. BMC
Endocr Disord 5:3. doi:10.1186/1472-6823-5-3.
13. El Maghraoui A, Mouinga Abayi DA, Ghozlani I, et al. Preva-
lence and risk factors of discordance in diagnosis of osteoporosis
using spine and hip bone densitometry. Ann Rheum Dis. In
14. Nelson DA, Molloy R, Kleerekoper M. 1998 Prevalence of oste-
oporosis in women referred for bone density testing: utility of
multiple sites. J Clin Densitom 1:5e11.
15. Kohrt WM, Snead DB, Slatopolsky E, Birge SJ Jr. 1995 Additive
effects of weight-bearing exercise and estrogen on bone mineral
density in older women. J Bone Miner Res 10:1303e1311.
16. Vokes TJ, Gillen DL, Lovett J, Favus MJ. 2005 Comparison of
T-scores from different skeletal sites in differentiating postmen-
opausal women with and without prevalent vertebral fractures.
J Clin Densitom 8:206e215.
17. Rand T, Seidl G, Kainberger F, et al. 1997 Impact of spinal de-
generative changes on the evaluation of bone mineral density
with dual energy X-ray absorptiometry (DXA). Calcif Tissue
18. Reid IR, Evans MC, Ames R, Wattie DJ. 1991 The influence of
osteophytes and aortic calcification on spinal mineral density in
19. El Maghraoui A. 2004 Osteoporosis and ankylosing spondylitis.
Joint Bone Spine 71:573e578.
20. El Maghraoui A, Borderie D, Edouard R, Roux C, Dougados M.
1999 Osteoporosis, body composition and bone turnover in
ankylosing spondylitis. J Rheumatol 26:2205e2209.
21. Maillefert JF, Aho LS, El Maghraoui A, Dougados M, Roux C.
2001 Changes in bone density in patients with ankylosing spon-
dylitis: a two-year follow-up study. Osteoporos Int 12(7):
22. El Maghraoui A, Do Santos Zounon AA, Jroundi I, et al. 2005
Reproducibility of bone mineral density measurements using
dual X-ray absorptiometry in daily clinical practice. Osteoporos
23. El Maghraoui A, Achemlal L, Bezza A. 2006 Monitoring of
dual-energy x-ray absorptiometry measurement in clinical prac-
tice. J Clin Densitom 9(3):281e286.
156 El Maghraoui et al.
Journal of Clinical DensitometryVolume 10, 2007