Background/Purpose

Diagnostic discordance for osteoporosis is the presence of different T-scores in two skeletal sites in the same subject leading to different WHO diagnostic categories. Discordance is defined as minor when the difference between two sites is no more than one WHO diagnostic class and major when one site is osteoporotic and the other is normal¹. This study examines to determine the percentage of minor and major diagnostic discordance and identify associated factors in patients undertaking osteoporosis screening.

Methods

Details of the first Dual-X-Ray-Absorptiometry test (DXA) during 2011-2013 were extracted, including weight, height, T score at femoral neck and total hip in the right side (RFN, RTH) and left side (LFN,LTH) and T score at lumbar spine (LS). Only complete data for individuals over 18 years old, with nationality of North Africa Middle East (as per WHO definition) were analysed. Differences in T scores and degree of discordance between sites were calculated. Age and BMI were analysed as contributing factors.

Results

One thousand, four hundred and forty four patients with complete data were identified. The mean age was 59.1 (±13.2 SD) and 86.3% were females. Diagnostic agreement among all skeletal sites was found in 415 (28.7%) patients, while 631 (43.7%) and 398 (27.6%) showed at least one major or minor discordance, respectively. Maximum concordance was found between right total hip and left total hip (86.6%) and minimum between lumbar spine and left total hip (40.7%). Minor discordance was present in about 40% of the patients when comparing spine to any hip site.  Major discordance in LS compared to all hip regions ranged from 19.2 to 21.3%. All comparisons of skeletal sites, including trend of direction is shown below in table 1. A significant correlation with discordance was observed with both age and BMI (p>0.001).

Conclusion

Results show a high level of major diagnostic discordance, higher than previously reported in published studies^1-3. This high prevalence of discordance could produce some problems for the physicians in decision-making regarding these patients. This reiterates the understanding that multiple site measurements are mandatory for osteoporosis diagnosis, including BMD measurements at both hips. High prevalence of discordance between lumbar spine and hip T-scores suggests some defects in the cut-off values for the definition of osteoporosis and osteopenia proposed by the WHO. BMD should be used as only one of the factors in making therapeutic decisions when evaluating patients with osteoporosis.

Table 1. Number (percentage) of cases categorised as normal, minor and major discordance and the directional trend and weight between the different skeletal sites.

		Discordance				Number of
Comparison	Normal	Minor	Major	Trend	Direction	comparisons
LS-RTH; n (%)	581 (41.2)	544 (38.5)	285 (20.2)	93.3%	LS lower	1410
LS-LTH; n (%)	570 (40.7)	532 (38)	298 (21.3)	93.7%	LS lower	1400
LS-RFN; n (%)	579 (40.9)	561 (39.9)	270 (19.2)	92.1%	LS lower	1407
LS-LFN; n (%)	575 (41.2)	469 (40.8)	242 (20.1)	89.5%	LS lower	1396
RTH-RFN; n (%)	1150 (80.9)	260 (18.2)	12 (0.9)	56.9%	RFN Lower	1422
LTH-LFN; n (%)	1097 (77.8)	297 (21)	16 (1.2)	67.9%	LFN Lower	1410
RTH-LTH; n (%)	1219 (86.6)	177 (12.6)	11 (0.8)	51.6%	RTH Lower	1407
RFN-LFN; n (%)	1121 (80)	261 (18.6)	19 (1.2)	64.3%	LFN Lower	1401
RTH-LFN; n (%)	1058 (75.4)	319 (22.7)	26 (1.9)	65.8%	LFN Lower	1403
RFN-LTH; n (%)	1085 (77.2)	297 (21.1)	23 (1.7)	56.5%	RFN Lower	1405

LS, Lumbar Spine. LTH, Left Total Hip. RTH, Right Total Hip. LFN, Left Femoral Neck. RFN, Right Femoral Neck

¹Mounach et al Semin Arthritis Rheum 2005

²O’Gradaigh et al Osteoporos Int 2003

³Woodsen et al Clin Densitom 2000

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/spine-hip-diagnostic-discordance-in-the-united-arab-emirates/