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Cardio Lipoprotein Panel


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Hi,  As a new PA there are topics that come I have such little experience with.  In PA school, the Cardiac lipoproteins weren't really discussed.  We were taught about the ATP III guidelines for treating cholesterol.  My SP orders the lipoproteins for all elevated LDL levels to help her determine if treatment is necessary.  I would love others opinions and experience with these.  I have read up on them and still unsure on using them in family practice to guide treatment rather than the ATP III guidelines.

She orders " Cardio IQ lipoprotein, hsCRP, homocysteine" . 

 

Thanks!!

 

 

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Alright, so here's how this works. 

 

You first look at the patient, whether they have known CAD or CAD equivalents such as diabetes, RA, SLE, etc. Really any known vascular disease for that matter. Then you look at family history. Does the patient have a family history of premature CAD? Long smoking history? If so, they're higher risk and you need their non-HDL (total - HDL) to be under 100 as this is a better predictor of MACE than LDL. If they're diabetic and even if they have okay cholesterol numbers, consider starting atorvastatin 10 or at least something with evidence (not zocor 10) as the heart protection study showed these people do better if they're on something. Remember, statins do more than lower cholesterol. They stabilize atherogenic plaques and decrease vascular inflammation. 

 

If the patient is indeed high risk or if you are on the fence about whether or not to put a patient on a statin, it's reasonable to order an Apo B and LDL-Particle number. Particle size doesn't mean anything, it's about particle number. As for Apo-B, each atherogenic particle has an Apo B attached to it and therefore it's a better predictor than non-HDL or LDL (LDL is a calculated value anyways). It's not uncommon for someone to have a non-HDL or LDL that's at goal but continue to have an elevated Apo B or LDL-particle number. If that's the case and they're high risk with known CAD, s/p bypass etc, switch them to a higher intensity statin or consider an add-on such as zetia. 

 

hs-CRP is simply a risk factor. Lots of things can elevate hs-CRP as you know, but we know that vascular inflammation portends a higher risk than someone who has normal inflammatory markers. This can be a target and can be treated with smoking cessation, fish oil, weight loss, controlling diabetes. 

 

Homocysteine is considered a cardiac risk factor, but to date there is no evidence that treating an elevated homocysteine leads to less cardiovascular events. 

 

If you're still on the fence after all of this, consider ordering a cardiac calcium score. For it to be of much value, men should be in their early 50s and females in their mid 50s. This tells you how much established calcification the patient has in their coronaries. Higher numbers = higher risk. There is no such thing as a false positive in this test but there can be false negs if the patient is too young or the plaques aren't established and calcified. If the patient has bad cholesterol numbers but a cardiac calcium score of 0 and they're 62, their ten year risk is very low and they may not need to have their cholesterol run as tight as someone with a cardiac calcium score of 800. 

 

Also, Lp(a) is a risk factor similar to hs-CRP. Patients with high Lp(a) have more atherogenic particles. This isn't a target, it's simply another risk factor. PCSK 9 inhibitors significantly reduce Lp(a). Statins not as much. 

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In most cases in a pt with a cardiac history, LDL and risk assessment then determine treatment.  There is increasing evidence of ApoB (and Apo A-I) being a useful cardiac marker, I would consider it in a pt with a cardiac history.  Poor evidence for homocysteine or any of the other cholesterol markers to guide treatment.  Threshold to start statin therapy should be low: they are usually well-tolerated and safe and proven to lower M&M by a ridiculous amount of studies.

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  • 1 year later...

These types of lipid markers are definitely becoming more mainstream and it's only a matter of time before insurance covers them more widely (assuming insurance even covers lab testing by then!). LDL-C seems more and more outdated when compared to measuring the numbers directly. Here's a good recent review on the more sophisticated lipid markers... hope it helps!  https://www.accesalabs.com/blog/ldl-particle-number-apob-test/

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