What is the CAROC Score?
CAROC (Canadian Association of Radiologists and Osteoporosis Canada) is a simplified fracture risk assessment tool that estimates 10-year probability of major osteoporotic fractures using only five variables: sex, age, femoral neck bone mineral density (BMD), prior fragility fracture, and glucocorticoid use. 1, 2
Risk Categorization
CAROC classifies patients into three 10-year fracture risk categories 2, 3:
- Low risk: <10% probability of major osteoporotic fracture
- Moderate risk: 10-20% probability
- High risk: >20% probability
The Society of Obstetricians and Gynaecologists of Canada (SOGC) uses these CAROC thresholds to guide treatment decisions, with moderate risk defined as 20% risk of major osteoporotic fracture (MOF) over 10 years or 3% risk of hip fracture, and very high risk defined as MOF >30% or hip fracture risk >4.5%. 1
How CAROC Works
The tool starts with basal fracture risk tables derived from Canadian FRAX probabilities, stratified by age, sex, and femoral neck BMD, then adjusts upward by one risk category if the patient has either a prior fragility fracture or prolonged glucocorticoid use. 2
Key operational features 2, 3:
- Does not require computer or web access - can be calculated manually
- Requires femoral neck BMD measurement - cannot be used without densitometry 3
- Limited to 5 clinical variables - simpler than FRAX which uses 11 variables
Performance and Validation
CAROC demonstrates good calibration to the Canadian population 2, 4:
- Observed 10-year fracture rates in validation studies: 6.1-6.5% in low-risk, 13.5-14.6% in moderate-risk, and 22.3-29.1% in high-risk individuals 2
- High concordance with FRAX: 88-89% agreement in risk categorization 2
However, FRAX provides incremental improvement in fracture prediction compared to CAROC, with net reclassification improvement of +2.8% (P<0.001), particularly among individuals who remain fracture-free. 5 The number needed to assess using FRAX instead of CAROC to yield one improved prediction is only 36 individuals overall, and as few as 4-8 in high-risk subgroups (prior fracture or prolonged glucocorticoid use). 5
Clinical Application Context
In real-world practice, CAROC and FRAX frequently produce discordant risk estimates in up to 52% of patients, with disagreement around the crucial 20% high-risk treatment threshold occurring in approximately 20% of cases. 4 This discordance stems partly from disagreement about fracture history between BMD reports and clinical assessment (present in 19.8% of patients). 4
Important Caveats
- CAROC was designed as a simplified alternative when full FRAX assessment is not feasible 2, 3
- The Canadian Association of Radiologists currently endorses CAROC for BMD reporting, though there is ongoing debate about potentially replacing it with FRAX in future guidelines 6
- CAROC requires accurate patient-reported history of prior fractures and glucocorticoid use, which can be prone to error 4, 6