Intro: Welcome to UAB MedCast, a continuing education podcast for medical professionals, providing knowledge that is moving medicine forward. Here's Melanie Cole.

Melanie Cole, MS (Host): Welcome to UAB MedCast. I'm Melanie Cole. And today, we're highlighting trabecular bone score. Joining me is Dr. Basma Abdulhadi. She's an endocrinologist, the Director of Bone Densitometry, and an Assistant Professor in the Division of Endocrinology, Diabetes and Metabolism at UAB Medicine.

Dr. Abdulhadi, thank you so much for joining us. I'd like to start with the definition of trabecular bone score and how it extends what we already know from DEXA. But before we do that, can you tell us a little bit? Give us a little overview of osteoporosis and how that contributes to bone density issues.

Dr. Basma Abdulhadi: Thank you so much, Melanie, for having me. Historically, we've defined osteoporosis as a skeletal disease that's characterized by low bone mass and microarchitectural deterioration resulting in increase bone fragility and susceptibility to fracture. We've typically used DEXA scan to define osteoporosis based on bone mineral density.

Bone mineral density is a measure of the quantity of mineral in the bone tissue. And we expressed that as a T-score comparing the patient's bone mineral density to that of young, healthy adults. So with bone mineral density, we're talking about quantity of bone. And what we've noticed in our patients is that a huge proportion of patients with osteoporosis-related fractures actually have BMD scores that are better than -2.5 or osteoporosis. So, we're seeing a lot of fractures in patients with osteo osteopenia or even low bone mineral density.

So, this is where trabecular bone score comes into play. So, trabecular bone score looks at bone quality. So, it's an indirect measure of trabecular microarchitecture or, to simplify it, the structural arrangement of trabeculae in the bone. So, this contributes obviously to bone strength, and it can give us information beyond what a regular T-score or bone mineral density can give us.

Melanie Cole, MS: Why do you feel it's so important that bone health clinicians care about TBS in addition to bone mineral density?

Dr. Basma Abdulhadi: So, trabecular bone score is important because it's been found to predict fracture risk independent of bone mineral density. TBS is a software essentially that we can add to our DEXA scan machines. And it analyzes the gray level textural patterns in the lumbar spine. So usually, we're looking at L1 to L4. When we talk about TBS, it's a number. Again, as I said, it's a unitless value. Higher values reflect more homogenous bone texture, and then lower values reflect more heterogeneous, weaker radicular structures.

We will be integrating TBS into our FRAX, so the fracture risk assessment score, and it'll adjust the FRAX upward or downward depending on its value. It's really useful to use TBS or to look at TBS-adjusted FRAX in patients with osteopenia or when their fracture risk is close to intervention, but it's not there yet. So, it can add additional information. It can increase the FRAX risk so that we decide to treat the patient, for example, if they're borderline without the TBS-adjusted frax. So, we're excited to be using it at UAB. We are typically going to include patients above the age of 40 with a T-score of -1.1 or lower.

Melanie Cole, MS: Then, Doctor, it seems particularly informative in conditions where bone mineral density underestimates risk, but are there populations where it has, in your mind, definitely earned its stripes, like type 2 diabetes or obesity, these sorts of things?

Dr. Basma Abdulhadi: So, it is very useful in patients with secondary osteoporosis and to your point, Melanie, patients with type 2 diabetes. We know that their BMD's typically 5-10% higher than patients without diabetes, and this higher BMD does not really translate to a lower fracture risk. We actually know that type 2 diabetics have increased fracture risk. So for a hip fracture, it's about 1.5 higher than non-diabetic patients of a similar age. So in patients with type 2 diabetes, TBS could be very useful because it can capture deterioration of bone quality that is not necessarily reflected in the BMD or T-scores.

Melanie Cole, MS: Well, there's been enthusiasm because you just mentioned around TBS and postmenopausal women, but what about men, especially older men? Is this a tool we're underutilizing in that population?

Dr. Basma Abdulhadi: So, we can use TBS in anyone above the age of 40, so men and women above the age of 40. BMI is an important aspect. We're only going to be using TBS for patients with BMI between 15 and 37 because the values can be reduced if there's excessive soft tissue in the abdomen. So, our DEXA scan technicians will be screening DEXA scans as they are doing them. Anyone above the age of 40 with osteopenia and the BMI between 15 and 37, we will be doing TBS-adjusted FRAX for those patients.

I will say that TBS has only been validated so far in initial diagnosis. So, this is something that we're only going to get on initial scans because it can help us in risk stratifying patients and help us decide whether we're going to treat a patient. We're not going to be monitoring TBS over time. There's a lot of interest in using TBS to look at response to treatment. There's been a few studies that looked at TBS changes with the anabolic management. So if someone's on teriparatide or abaloparatide, TBS can improve. In patients on antiresorptive therapy, so Reclass or Fosamax or bisphosphonates, we don't really see a change in TBS values. So in the future, we might be using TBS to monitor treatment, anabolic therapy response.

Melanie Cole, MS: Doctor, if you were advising organizations like the National Osteoporosis Foundation today, would TBS integration be something that you would advise them used in clinical pathways? Would it be a recommendation or a mandate? What would you advise?

Dr. Basma Abdulhadi: I think it's very useful to use TBS, because it provides complementary but actually independent information about fracture risk assessments. So, the best thing to do is to combine both parameters to get a more comprehensive view of the patient's bone health. So, BMD and TBS are complementary. They both provide valuable information. TBS is going to be very important in patients who are borderline cases where the patient's fracture risk estimate puts them at the threshold of treatment. In these situations, TBS will be very important because it might reclassify patients either above or below the treatment threshold.

So, it might help you make a decision to start patient on therapy versus holding off and monitoring. So, I think that's really where it adds a lot of value in these borderline cases. And it can really help drive management decisions. I will say it should not be used alone for diagnosis. So if someone has a low TBS score, we can't really use that to say, "Okay, we're going to start the patient on therapy." But I think when we use it in addition to BMD, it's going to provide a lot of valuable information.

I don't think we've talked about the numbers of TBS. Again, TBS is unitless. So, it's just going to be a number that shows up. Anything above 1.3 is going to be normal TBS value or normal bone microarchitecture. Anything less than 1.2 is considered degraded microarchitecture. And then, anything in between is partially degraded.

Melanie Cole, MS: Doctor, this is really an interesting prospect, this TBS, and the implications for it. So, what's the most important piece of clinician education that you feel we haven't nailed yet about trabecular bone score, the things that you wish every practitioner understood before they start using it?

Dr. Basma Abdulhadi: I think one of the important things to remember is TBS can independently predict fracture risk. It's been validated in multiple cohort studies, and it can predict both vertebral and non-vertebral fracture. It is important to note that it can be used solidly or independently to diagnose osteoporosis. So, we're still going to rely on DEXA scan, BMD T-scores to diagnose osteoporosis. The best way to use TBS is to use it to complement BMD DEXA scan findings. So, combining both parameters is going to give us the best idea of the patient's bone health. Most useful to use TBS in patients with secondary osteoporosis. So again, it provides valuable information in patients with type 2 diabetes, patients on steroids, patients with hyperparathyroidism.

And I think the most important clinical implication for FRAX-adjusted TBS is really in patients with borderline cases where, you know, they're at the cusp of the threshold to initiate pharmacological therapy. In those patients, it might reclassify them as either above or below the treatment threshold, and this might alter clinical management.

Melanie Cole, MS: Thank you so much, Dr. Abdulhadi, for joining us today and sharing so much great information for other providers. And for more information, you can always visit our website at uabmedicine.org/physician. That concludes this episode of UAB MedCast. I'm Melanie Cole