What Should Sickle Cell Patients Know About Lab Test Ranges?
More Programs and Publications Featuring Maya Bloomberg, MSN, APRN
In this program:
Sickle cell laboratory reference ranges may vary, so what’s essential for SC patients to know about testing? Hematology nurse practitioner Maya Bloomberg from Sylvester Comprehensive Cancer Center explains lab test reference ranges, factors involved in setting ranges, racial and health disparities, and actionable advice for patients.
Transcript
Interviewer:
How are laboratory reference ranges determined as it relates to sickle cell? And are they any ranges or values that do you think are under scrutiny or should have further research to validate them?
Maya Bloomberg, MSN, APRN:
So each lab establishes its own reference ranges, which are really designed to reflect what is typical based on age, gender, and other factors. Now these reference ranges have been under scrutiny since it can lead to misdiagnosis, under or over diagnosis, and delayed treatment, all can which further contribute to health disparities. There used to be racial differences in hematologic values, which have recently been changed, sometime during the pandemic, because there had been some studies showing that African Americans tended to have lower than average hemoglobin levels, but now we see the same reference ranges in our labs. There have also been variations on creatinine level and glomerular filtration rate, also known as GFR, and these are two tests that evaluate kidney function. So the argument was that these race-based reference ranges could lead to again to that underdiagnosis of true disease states like anemia and kidney disease, which could then lead to the delay in treatment. So we're now acknowledging that these racial disparities are often due to systemic racism as opposed to genetics itself.
Interviewer:
And I actually did some research on what the average range is for hemoglobin for SCD patients, which is 7 to 11, but I was actually trying to look up what it is for sickle cell trait patients, or if there is any kind of reference to it at all? And I couldn't really find anything, but my question here is, does this demonstrate to you a lack of monitoring in sickle cell trait patients perhaps, or is this something that you've noticed in your experience?
Maya Bloomberg, MSN, APRN:
Well, in theory, individuals with sickle cell trait, we would expect them to have the same values as somebody without sickle cell trait. With regards to the range of 7 to 11 for hemoglobin level for sickle cell disease, it'd be interesting to further break that down by subtype or your hemoglobin genotype, because obviously hemoglobin SC or S beta-thal plus is going to have a higher hemoglobin while hemoglobin SS and S beta-thal zero are going to have lower hemoglobin. When I was thinking of this question, I was thinking more about just the actual reference range for hemoglobin and creatinine, and a couple other markers varied if you were African American versus Caucasian or Asian, just from old literature. So I think that's what is starting to change there. There's a Joel Burvell, he is on social media, I found him on TikTok, and he does so much on health and racial disparities, and he's the first one who had highlighted the disparities and I think was actually part of the reason why the hemoglobin values have thus changed, because several years ago, if you were looking at Medscape, for example, they had different values for hemoglobin depending on your race, which are now no longer present.
Interviewer:
What CBC values should sickle cell patients focus on that often deviate from the baseline?
Maya Bloomberg, MSN, APRN:
Sure. So I'm going to cover CBC, but then I'm also going to cover a couple other ones. And I think this is a very important reason to know what your baseline is and what your normals are. So if something deviates, you can have an idea and know how to really stand up and advocate and speak up for yourself. The first thing that's very important to know is just what's your baseline hemoglobin. Because if I have a person in the emergency room, I see their hemoglobin's 6, if that individual is like, “Oh, my baseline hemoglobin is 7,” that's going to be much less concerning than somebody whose baseline hemoglobin was 9.5 and having over three gram decrease. So knowing what your baseline hemoglobin is really helpful for in the acute setting, but it's also helpful if you're starting any new type of medication that might modify your disease, such as with hydroxyurea or a newer medication called voxelotor, also known as Oxbryta, which can help raise your hemoglobin.
So knowing that baseline and being able to track changes is a positive. Your white blood cell count is another important one. White blood cells can indicate infection, but also during a sickle cell crisis, since it's an inflammatory state, you can actually see your white cell count increase. So if you're seeing your white cell count always high, first of all, you want to rule out infection. Do you have any respiratory symptoms, any runny nose, any urinary symptoms that could indicate an infection? And then once that's ruled out, then we can see, okay, it might be related to your sickle cell and your sickle cell pain episodes. When we put patients on hydroxyurea, hydroxyurea I mentioned raises your hemoglobin, but it also decreases your white cell counts and your platelet count, which is actually a positive thing because your white cell and your platelet counts are very sticky cells. And when you're having a sickle cell crisis, they can worsen the blockage of blood flow, which then will worsen the pain. So hydroxyurea can decrease this. And interestingly, in the research...
Hydroxyurea (Hydrea) raises your fetal hemoglobin production and fetal hemoglobin is the primary hemoglobin produced by babies in utero. And then at around six to 12 months of ages, is when your adult hemoglobin takes off and when you can start seeing sickle cell issues. But in the hydroxyurea clinical trials, when they looked at fetal hemoglobin level, they would pair patients with the same exact fetal hemoglobin level and those individuals who had lower white cell counts, and I'm saying lower end of normal, not out of the normal range, they ended up doing clinically better than those with a higher white cell count with the same fetal hemoglobin. So white cell count is definitely something you want to monitor and if you're seeing it's constantly elevated, that would be an indication, maybe you'd benefit from hydroxyurea, but something to talk to your provider about.
Since hydroxyurea can reduce your white cell count and platelet count, you also want to make sure it doesn't reduce it too much, so one of the other differentials that we look at is your absolute neutrophil count. So if your absolute neutrophil count were to fall below 1000 for example, that would be an indication to hold the hydroxyurea because it might be negatively affecting your bone marrow, but then we would restart once everything recovers.
Another CBC value is your MCV, your mean corpuscular volume. This represents the size of your hemoglobin. Now in sickle cell, most patients will have a normal MCV and a normal size of your red cell. Individuals on hydroxyurea, it will make your MCV high, above 100, and this lets me know that you're taking your medication. So when I look at my patient's CBC and they're on hydroxyurea and I see them having a normal MCV, I ask them, "Are you taking your medication regularly or are you missing any doses?" Because if they're not missing any doses, that would be an indication potentially to raise the dose further.
Platelet counts is another one on CBC that you want to look at, this is another acute phase reacting, just like your white blood cell count, which can rise during a sickle cell crisis, again, very sticky, it can worsen the blood flow. So you want to monitor for your platelet counts and just again, if it's always elevated, that is an indication that you're just constantly having some inflammation from a sickle cell going on internally and would want to address that, because if your platelet count's super high, that can be a risk for thrombosis or for blood clots.
On the other end, if your platelet count is very low, that can be a bleeding risk and people, they say with hemoglobin SC, they can have an enlarged spleen, which a lot of times will pool the platelets and we'll see low platelet count as a result of that. We don't usually start any treatment for low platelet counts until you're below 30,000, so if you're at 100,000, I don't want you to be concerned, but it's important to know signs of bleeds, if you're having nose bleeds or gum bleeds or easy bruising, heavy periods with a low platelet count, that would definitely be something you want to discuss with your provider.
Now, switching to a metabolic panel, I would recommend knowing what your bilirubin level is and knowing what your normal is, because when your body is breaking down red blood cells, bilirubin is a by-product, and that's what contributes to jaundice or yellowing of your eyes, which is literally the only visible symptom of sickle cell. So if you're noticing worsening of your jaundice or worsened yellowing of your eyes, you want to pause and think, "What am I doing that might be contributing to this? Is it a matter of me needing to drink more water? Am I overdoing it and need to rest? Do I need to manage my stress and start saying no or asking for help? And kind of looking in to see what that might be.
Your reticulocyte count is what reflects your immature hemoglobin in red cells. So when you have a low hemoglobin, your body should compensate by producing new hemoglobin, and that's what's reflected with an elevated reticulocyte count. If you have a low hemoglobin and a low retic count, then that's concerning because that's telling you that your body is not compensating appropriately and producing new hemoglobin, so we'd want to look into why that is.
If you have any kidney disease, that can contribute to a low reticulocyte count, because your kidneys are what secrete a precursor to producing new hemoglobin called erythropoietin. So say you have focal glomerular sclerosis or FSGS and you have low hemoglobin, it's important to check an erythropoietin level, because if your erythropoietin level is low in relation to what your hemoglobin level is, we could potentially improve that with an additional medication. So it's very important to just know what your normals are, know what your baseline hemoglobin is, so that way if you're in the hospital setting or if you're starting a new medication, you have an idea of when things are improving or getting worse, and can really just advocate for yourself knowing what those normal ranges are.
Interviewer:
So if reticulocyte is typically high for sickle cell patients, is there, I guess, a cut-off to what high is too high or not high enough or...if that makes any sense?
Maya Bloomberg, MSN, APRN:
Yeah, no, that makes sense. So I'm sure that there's countless warriors who are in the hospital and they're like, "Oh, your labs look normal, you can't be in such severe pain," and a lot of times they'll look at your hemoglobin level, they'll look at your bilirubin and they look at your retic count. So if your retic count isn't super high, you might be questioned and say, "Oh, you're not sickling that much," but the reality is, is that say somebody with hemoglobin SC who starts with a higher baseline hemoglobin, we wouldn't expect to see that high retic count and that impressive anemia when they're having a sickle cell crisis.
Now, for individuals who just chronically have a super high retic count, that means your bone marrow is having a lot of stress on it, just having to constantly crank out these medications and that kind...medications, cranking out these new red blood cells, and over time, you can then get more organ dysfunction and whatnot. So it's just very important to track this, because if you're just always 25 percent and extremely high, you just want to make sure that we're managing and optimizing your sickle cell, because that would be assigned to me that we need to do something to stabilize your hemoglobin a little bit better.
Interviewer:
And I think it's important that we acknowledge that sickle cell isn't uniform across the board. There's different types of sickle cell, there's different manifestations of sickle cell that you've outlined in this, so I think it's really important for patients to understand that their version of sickle cell is completely different to someone else's, and that will reflect in their blood work, it will reflect in their symptoms and things like that.
Maya Bloomberg:
And we need the providers to understand that as well.
Interviewer:
Yes, very much so.
Maya Bloomberg, MSN, APRN:
And not try to have a cookie cutter for what a sickle cell crisis looks like that and just believe the patients when they say that they're having severe pain.
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