Clues to your REMS and DXA Reports- what data is important and how to look for patterns and consistency.
The goal of this post is to help you better understand your REMS report so that the information on the report is useful to you as you make decisions about your bone health care. It needs to be emphasized that the intent is not to teach you how to interpret the report - interpretation of any medical report should be done by a medical provider. However, a better understanding of what the numbers on a REMS report mean would lead to a more fruitful conversation with your health care provider.
There will be information on both REMS and DXA reports that are similar - BMD (g/cm2) T-score, Z-score and the diagnosis based on the T-score. Both REMS and DXA have been determined to be a clinically valid means of determining BMD and T-score values and therefore in diagnosing and monitoring osteoporosis (please refer to the post: "alphabet soup of densitometry" )
A general and basic principle that applies when reviewing not only densitometry reports, but any medical report, is that it needs to make sense. The numbers on a report should fall into certain patterns that have a logical consistency. An example of this consistency are the T-score values. In an otherwise healthy individual there should be uniform distribution of bone mass and therefore, the T-score values should be concordant (similar) and not discordant (dissimilar) between the different Regions of Interest (ROIs). The International Society of Clinical Densitometry (ISCD) recommends that the T-score values of the spine and hips should be within one Standard Deviation of one another. In certain pathological conditions (i.e., transient osteoporosis of pregnancy and lactation) or the presence of certain disease processes (i.e., certain cancers, metastatic disease or metabolic bone diseases), there can be localized affects on bone mass resulting in T-score discordance.
There are other patterns that also should be evaluated. Based on ISCD guidelines, the individual T-score values of the individual vertebral bodies are not relevant to diagnosing or treating osteoporosis - it is the averaged T-score value of all of the vertebral bodies examined. Also, at least two vertebral bodies must have been successfully evaluated for test to be considered valid. Therefore, the results of a single vertebral body cannot be used for establishing a diagnosis.
In the spine, the BMD values of the individual vertebral bodies should increase from L1 through L4. There are some cases where that pattern does not happen and there are ISCD guidelines for those situations. In general, if one of the BMD values is out of line with the others, it should not be excluded when calculating the average spine BMD. The Total Spine BMD (the average of the individual vertebral body BMD values) is used to determine the T-score, Z-score and diagnosis.
In the hips, the Femoral Neck (or Neck) BMD and the Total BMD are important values. The Neck BMD should always be smaller than the Total BMD. A Neck BMD value that is larger than the Total BMD is most likely due to technical error such as inappropriate hip positioning. Only a very small percentage of the cases are due to a physiologic problem with the bone. Toal Hip BMD values, by convention, are also used to determine changes in bone mass between sequential test. When comparing serial DXA results it is important to remember that only DXA scans performed on the same machine and preferably by the same examiner will be meaningful. DXA-derived BMD is converted to T-scores using the different manufacturers’ proprietary databases, DXA scans performed on different manufacturers’ machines cannot be quantitatively compared. There is at least a 10% discrepancy between the Hologic and GE spinal databases. Trochanteric BMD values are more of a historic relic and are not used in the determination of diagnoses.
When using REMS, comparisons can be made without regard to where or who did the study - the documented rates between different users and between different EchoS units are extremely small.
REMS-derived BMD and DXA-derived BMD values should not be compared quantitatively; but a qualitative comparison is reasonable. Unfortunately, in general REMS and DXA BMD values will often be dissimilar (discordant). This may be due to many different reasons, but in most situations, DXA examinations will be inappropriately done due to technical error, artifactual error, calibration error, and/or suboptimal positioning. DXA has a 40-50% error rate in determining BMD in the general clinical setting. In those cases, it is the responsibility of the provider to look at the numbers and see which ones make more sense.
Unless the DXA study happens to include a TBS, then there is no more significant information on a DXA scan. However, the REMS test will provide a Fragility Score which is an assessment of bone strength.
The Fragility Score is determined from the sound waves that carry information on the structural properties of bone. It is presented on a graph on the second page of the REMS report that depicts a database of individuals who have or who have not sustained a fragility fracture. The colors differentiate those individuals who have sustained a fragility fracture from those who have not; the red zone represents individuals who have fractured, and the green zone represents individuals who have not fractured. The red and green zones are absolute. Everyone has fractured in the red zone, and no one has fractured in the green zone. The yellow zone represents red and green overlap – there is a mix of red and green underneath the yellow. Therefore, the yellow zone represents an area of statistical uncertainty in fracture risk assessment. Fracture risk is considered to be low in the yellow zone near the green but high in the yellow zone near the red. Therefore, fracture risk increases as the yellow zone is traversed from green to red.
One last important piece of information offered by the REMS assessment is 5-year fracture risk assessment. The Fracture Risk Score can help your provider advise you to fracture risk and recommendations for treatment.
Hopefully, this explanation on how the different measured values derived from a bone densitometry can be assessed and understood. Again, the purpose of this post was to provide some insight and education into how your provider may look at the numbers in either a DXA or REMS report - however, you still need your provider to help you interpret the results in order to help you decide on the best bone health plan for you.
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