Fahrenholtz Samuel J, Long Jeremiah R, Whitaker Michael D, Sensakovic William F
Section of Diagnostic Physics, Department of Radiology, Mayo Clinic Arizona, Scottsdale, Arizona, USA.
Section of Musculoskeletal Radiology, Department of Radiology, Mayo Clinic Arizona, Phoenix, Arizona, USA.
Med Phys. 2023 Mar;50(3):1623-1634. doi: 10.1002/mp.16057. Epub 2022 Oct 27.
Dual-energy X-ray absorptiometry (DXA) is an exam that measures areal bone mineral density (aBMD) and is regularly used to diagnose and monitor osteoporosis. Except for exam quality issues such as operator error, the quantitative results of an exam are not modified by a radiologist or other physician. DXA cross-calibration errors can shift diagnoses, conceivably leading to alternate intervention decisions and patient outcomes.
After identifying and correcting a cross-calibration bias of 3.8% in our two DXA scanners' aBMD measurements, we investigated misdiagnosis rates for given cross-calibration errors in a single patient cohort to determine the impact on patient care and the value of cross-calibration quality control.
The studied cohort was 8012 patients of all ages and sexes with femoral neck exams that were scanned on a single DXA unit from October 1, 2018 to March 31, 2021. There were six subcohorts delineated by age and sex, three female groups and three male groups. Data reporting focused on the highest risk subcohort of 2840 females aged 65 or older. The DXA unit had no calibration changes during that time. Only one femoral neck-left or right-was randomly chosen for analysis. Patients with multiple qualifying exams within the time interval had one exam randomly chosen. The proof-of-principle simulation shifted the aBMD values within a range of ±10%, ±8%, ±6%, ±4%, ±3.5%, ±3%, ±2.5%, ±2%, ±1.5%, ±1%, ±0.5%, and 0 (no shift); the cross-calibration shifts were informed by published results and institutional experience. Measurement precision was modeled by randomly sampling a Gaussian distribution characterized by the worst acceptable least significant change (LSC) of 6.9%, with 100 000 samplings for each patient. T-scores were recalculated from the shifted aBMD values, followed by reassigned diagnoses from the World Health Organization's T-score-based scheme.
The unshifted original subcohort of women aged 65 and older had 599 normal diagnoses (21.1% of the cohort), 1784 osteopenia diagnoses (62.8%), and 455 osteoporosis diagnoses (16.1%). Osteoporosis diagnosis rates were highly sensitive to aBMD shifts. At the extrema, a -10% aBMD shift led to +161% osteoporosis cases, and a +10% aBMD shift led to -64.5% osteoporosis cases. Within the more plausible ±4% aBMD error range, the osteoporosis diagnosis rate changed -10.5% per +1% aBMD shift as indicated by linear regression (R = 0.98). Except for the men aged 49 years and younger subcohort, the total cohort and five subcohorts had fit line slopes ranging between -9.7% and -12.1% with R ≥ 0.98. Cross-calibration bias had greater influence for diagnosis count rates compared to measurement precision, that is, LSC.
These results quantify the degree of misdiagnosis that can occur in a clinically relevant cohort due to cross-calibration bias. In medical practices where patients may be scanned on more than one DXA unit, ensuring cross-calibration quality is a critical and high-value quality control task with direct impact on patient diagnosis and treatment course. The clinical impact and incidence of poor DXA quality control practices, and cross-calibration in particular, should be studied further.
双能X线吸收法（DXA）是一种测量骨面积密度（aBMD）的检查方法，常用于诊断和监测骨质疏松症。除了诸如操作员失误等检查质量问题外，检查的定量结果不会因放射科医生或其他医生而改变。DXA交叉校准误差可能会改变诊断结果，这可能会导致不同的干预决策和患者治疗结果。
在识别并纠正了我们两台DXA扫描仪aBMD测量中3.8%的交叉校准偏差后，我们在单一患者队列中研究了给定交叉校准误差下的误诊率，以确定其对患者护理的影响以及交叉校准质量控制的价值。
研究队列包括8012名各年龄和性别的患者，他们在2018年10月1日至2021年3月31日期间在一台DXA设备上进行了股骨颈检查。根据年龄和性别划分出六个亚组，三个女性组和三个男性组。数据报告聚焦于2840名65岁及以上女性这一最高风险亚组。在此期间，DXA设备未进行校准更改。仅随机选择一侧股骨颈（左侧或右侧）进行分析。在该时间间隔内进行多次合格检查的患者，随机选择一次检查。原理验证模拟在±10%、±8%、±6%、±4%、±3.5%、±3%、±2.5%、±2%、±1.5%、±1%、±0.5%和0（无偏移）范围内改变aBMD值；交叉校准偏移是根据已发表的结果和机构经验确定的。通过对以6.9%的最差可接受最小显著变化（LSC）为特征的高斯分布进行随机抽样来模拟测量精度，对每位患者进行100000次抽样。根据偏移后的aBMD值重新计算T值，然后根据世界卫生组织基于T值的方案重新分配诊断结果。
65岁及以上女性的未偏移原始亚组中有599例正常诊断（占队列的21.1%），1784例骨量减少诊断（占62.8%），455例骨质疏松症诊断（占16.1%）。骨质疏松症诊断率对aBMD偏移高度敏感。在极端情况下，aBMD降低10%会导致骨质疏松症病例增加161%，aBMD升高10%会导致骨质疏松症病例减少64.5%。在更合理的±4% aBMD误差范围内，线性回归表明（R = 0.98），每aBMD升高1%，骨质疏松症诊断率变化-10.5%。除了49岁及以下男性亚组外，整个队列和五个亚组的拟合线斜率在-9.7%至-12.1%之间，R≥0.98。与测量精度即LSC相比，交叉校准偏差对诊断计数率的影响更大。
这些结果量化了由于交叉校准偏差在临床相关队列中可能发生的误诊程度。在患者可能在多个DXA设备上进行扫描检查的医疗实践中，确保交叉校准质量是一项关键且具有高价值的质量控制任务，直接影响患者的诊断和治疗过程。DXA质量控制不佳的临床影响和发生率，尤其是交叉校准方面，应进一步研究。
