Parameter(z): LV Mass Z-Scores

LV Mass Z-Scores

...these could easily be included in echocardiography software, which would allow automated generation of an LV mass-for-height z score and percentile for each child undergoing echocardiography.

LV mass was estimated by M-mode echocardiography in 440 healthy nonobese reference children (birth to 21 years) from Boston Children's Hospital.

References

A novel method of expressing left ventricular mass relative to body size in children. Foster BJ, Mackie AS, Mitsnefes M, Ali H, Mamber S, Colan SD. Circulation. 2008 May 27;117(21):2769-75.

Comments (18)

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+8 Vote up Vote down

Steven Colan · 809 weeks ago

Wow! I cannot believe you have implemented that method that the authors showed to be inferior rather than the LMS method, which was the whole point of this article. This is really misleading.

2 replies · active 807 weeks ago

+7 Vote up Vote down

DanDan 46p · 809 weeks ago

It is not my intention to mislead.
The code that runs this calculator can be viewed here. Basically, it works like this:

create several arrays from the published data(1), one each for height, lambda (L), mu (M), and sigma (S)
lookup the L,M, and S values based on the height
enter values into the published z-score formula(2)
write the z-score
re-arrange and solve the equation for known z-score values (minus 1.65 and plus 1.65)
write the upper and lower limit values
write the mean (M) value

(1) I used the provided Data Supplement for the L,M,S values.
(2) z-score = [((LVM / M)^L) – 1] / (L · S)

I will continue double and triple-checking the data and routine in an effort to understand your criticism, but for the time being I admit to being quite baffled by this comment (not that this is anything new; I am frequently and easily baffled, perplexed, and distracted).

+7 Vote up Vote down

DanDan 46p · 807 weeks ago

I re-wrote the calculator: LMS LV Mass Calculator, v.4.

The updated JavaScript is here: lmsArray.js.

The results are the same.
I appreciate the scrutiny, but I just don't see the problem.

+7 Vote up Vote down

Viv Hunter · 786 weeks ago

I have independently tested this z-score calculator using the method described by Foster et al in their article: A novel Method of Expressing Left Ventricular Mass relative to Body size in Children.

Using the formula: z-score = [(LVMobs / M)^L – 1] / (L • S), and the values of M, L and S found in the data supplement of the same article, I found my independently calculated z score values to be exactly the same as those that calculated on this website.

Thus this site does not index LV mass to height^2.7, but rather uses the centile method described in the above mentioned article.

1 reply · active 785 weeks ago

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DanDan 46p · 785 weeks ago

Thanks for the comment and the verification, Viv.

Thanks also for pointing out what has to be the primary source of confusion: the z-scores are NOT indexed (see this post).

I have also created an interactive worked example to settle any further doubt about the nature of these calculations.

+6 Vote up Vote down

AKS · 740 weeks ago

If you calculate LVM by a 2D formula, LVM= 1.05{[5/6A1(L+t)] - [5/6A2L]}, could that be used to obtain a Z-score from this calculator? Or do you have to calculate the LVM by M-mode to use this calc?
Thanks.

1 reply · active 108 weeks ago

+7 Vote up Vote down

DanDan 46p · 740 weeks ago

The lv mass z-scores are derived from m-mode measurements. So, to be proper about the whole matter they probably should not be mixed with 2D LV mass measurements.

HTH,

Dan

+6 Vote up Vote down

Sarita · 512 weeks ago

Thanks for this post. It is really interesting,which have written over here. Keep posting.

+7 Vote up Vote down

my essay.biz · 482 weeks ago

It is a nice calculator for the LV mass Z-score. Your detail about it is so good and easy to understand. I like to find it here as it is helpful to know about the way it calculate the value.

+6 Vote up Vote down

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+3 Vote up Vote down

allmobitools · 300 weeks ago

Your website is so informative and this article is very helpful. I will visit again on your site in future.

+3 Vote up Vote down

Dr Sunil Kumar Rao · 293 weeks ago

any please explain the color code of Z score values.

0 Vote up Vote down

anusha · 135 weeks ago

Thanks for sharing a beautiful content, your content is always out of the world and must be learned by every healthcare professionls.
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