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Where can I find z-scores? [message #51] Mon, 18 February 2013 16:46 Go to next message
DHS user is currently offline  DHS user
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Is there a separate child dataset available that contains z-scores for stunting, wasting and underweight. Thank you!

[Updated on: Thu, 21 February 2013 10:03] by Moderator

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Re: Where can I find z-scores? [message #91 is a reply to message #51] Thu, 21 February 2013 10:11 Go to previous messageGo to next message
Liz-DHS
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Dear User, HC70 to HC73 and HW70 to HW73 were introduced to the recode definition to store the standard deviations of the new WHO child growth definition. Essentially all files using the DHS-5 recode structure have these variables.

[Updated on: Thu, 21 February 2013 10:19]

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Re: Where can I find z-scores? [message #127 is a reply to message #51] Mon, 18 March 2013 16:42 Go to previous messageGo to next message
Reduced-For(u)m
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If you are a STATA user, there is a new package called "haz06" which you can install that will calculate the WHO standards using the height and age variables, which is particularly convenient when you are using older DHS surveys that only have the old standards. You have to be careful that you are using age and height in the right units (months and cm - I think).

If any of the mods/DHS people know something I don't know about this package, I'd be very happy to hear, but it seems to work pretty well for me, and the new standards are a lot more consistent across age (especially at the over/under 24 month cut) than the old ones, at least for populations with mean HAZ below -1 (like most of the populations the DHS covers).
Re: Where can I find z-scores? [message #130 is a reply to message #127] Mon, 18 March 2013 17:29 Go to previous messageGo to next message
Trevor-DHS is currently offline  Trevor-DHS
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For older DHS recode datasets there are also separate datasets available for download that contain the variables based on the WHO child growth standards. These datasets are listed as "Height and Weight Scores - WHO Child Growth Standards" in the list of datasets available for download.
Re: Where can I find z-scores? [message #135 is a reply to message #91] Mon, 18 March 2013 20:04 Go to previous messageGo to next message
Kwesi.Nkrumah is currently offline  Kwesi.Nkrumah
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Hello,

Alternatively you can use the a stata ado called igrowup, developed by WHO and based on the Multi-Growth Reference study. You can find it on WHO website together with it manual. This will help you to calculate the anthropometric indices your self if you so wish.

Thank you very much
Re: Where can I find z-scores? [message #188 is a reply to message #91] Fri, 22 March 2013 16:22 Go to previous messageGo to next message
mdma0011 is currently offline  mdma0011
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HW70 Ht/A- stunting
HW72 wt/ht- wasting
HW71 wt/A- underweight
we know that ''A child is considered short for its age or stunted if its height-for-age Z-score is below minus two standard deviation (SD) from the median of the reference population''.

here in DHS if we code HW70 < -200 ; does it indicate stunted children ???
Re: Where can I find z-scores? [message #232 is a reply to message #188] Sat, 30 March 2013 00:14 Go to previous messageGo to next message
Reduced-For(u)m
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Yeah. The DHS reports the HAZ/WAZ/WHZ as standard deviations * 100, so -2sd is -200 here. I usually convert them back for graphs and figures, just so all the units are comparable to other work.

Just be careful when you are writing your definition that you don't accidentally make the missing values equal to 1 or 0, which can happen in certain environments.

So, in Stata, just to be sure, I would code:

gen stunted = HW70<=-200
replace stunted = . if HW70==.

There are other ways to do that, but that's one example. Also, I'm not technically sure if -2 exactly is stunted or not. It should matter very little, but the question is whether to code "<" or "<=". Someone from DHS know the answer to that?

Re: Where can I find z-scores? [message #236 is a reply to message #91] Sat, 30 March 2013 05:12 Go to previous messageGo to next message
alimnoushad is currently offline  alimnoushad
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The WHO has introduced a software called WHO Anthro. By using the Anthro anyone can easily calculate Z scores on the NCHS and new WHO growth standard.

786
Re: Where can I find z-scores? [message #2546 is a reply to message #127] Thu, 10 July 2014 10:01 Go to previous messageGo to next message
giacomo is currently offline  giacomo
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Reduced-For(u)m wrote on Mon, 18 March 2013 16:42

If you are a STATA user, there is a new package called "haz06" which you can install that will calculate the WHO standards using the height and age variables, which is particularly convenient when you are using older DHS surveys that only have the old standards. You have to be careful that you are using age and height in the right units (months and cm - I think).


Forgive me for contributing to a very old post, but my problem is related to this and in the future others may have the same issue.

I need to construct HAZ scores based on 2006 WHO standards for old rounds of the DHS data. To test the "zscore06" package in STATA I first tried to replicate the HAZ score provided by DHS in a recent dataset (Round V). The results I obtained for some observations are substantially different. I read the help provided with the package and the code (and variables' units) I used should be correct. Has anyone had experience on successfully replicating the HAZ scores with the "zscore06" package?

For your info, this is the code I used in a children dataset:

gen hw2_2 = hw2/10           /// Convert weight in Kg
gen hw3_2 = hw3/10           /// Convert height in cm

zscore06, a(hw1) s(b4) h(hw3_2) w(hw2_2)

gen HAZ = haz06 * 100

list HAZ hw70



Many thanks,
Giacomo

[Updated on: Thu, 10 July 2014 10:41]

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Re: Where can I find z-scores? [message #2548 is a reply to message #2546] Thu, 10 July 2014 13:20 Go to previous messageGo to next message
Trevor-DHS is currently offline  Trevor-DHS
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Hi Giacomo,

A couple of notes for you:
1) You don't need to compute the z-scores for older rounds of data. The Z-scores for the older rounds of surveys are available in separate data files that can be downloaded. These are the HW (Height and Weight scores) files, for example for Benin 2001 the file is BJHW41xx.zip (where xx is the type of data file).
2) The reason you are not matching the z-scores in the DHS data is because of the calculation of age used in the computation of the Z-scores. HW1 only gives age rounded off to the month, but in the calculation of the z-scores we compute age to the day, as follows:

* Calculate measurement date in days
gen mdate = mdy(hw18, hw17, hw19)
* Calculate birth date in days
gen bdate = mdy(b1, hw16, b2) if hw16 <= 31
replace bdate = mdy(b1, 15, b2) if hw16 > 31
* Calculate age in months with days expressed as decimals.
gen age = (mdate-bdate)/30.4375
* Compute Z-scores
zscore06, a(age) s(b4) h(hw3_2) w(hw2_2)

Note, though that the zscore06 software does not handle some of the flagging of data that we do, so you will find some differences related to flagged cases and to cases where the data of birth was imputed (where b10 != 1).

I hope this helps.
Re: Where can I find z-scores? [message #2549 is a reply to message #2548] Thu, 10 July 2014 13:32 Go to previous messageGo to next message
giacomo is currently offline  giacomo
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Dear Trevor,

That is a very exhaustive reply! Thank you very much for your help. I am aware of the separate files for HW scores but I initially thought would have been easier to compute the score in Stata. However, you raised a good point about the flagging.

Thank you again,
Giacomo

Re: Where can I find z-scores? [message #12340 is a reply to message #2549] Wed, 03 May 2017 09:42 Go to previous messageGo to next message
Gowokani is currently offline  Gowokani
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Giacomo

Any luck with the dofile of how to generate the HAZ, WAZ, and WHZ using this methord for ealier versions of DHS?

Gowo


Gowokani Chijere Chirwa
Re: Where can I find z-scores? [message #12341 is a reply to message #12340] Wed, 03 May 2017 13:15 Go to previous messageGo to next message
Trevor-DHS is currently offline  Trevor-DHS
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I'm not sure what exactly you are looking for. We have no additional dofile - we don't use Stata as the standard software for most of our processing. I recommend either using the downloadable datasets we have already produced, or calculating the scores as given earlier.

[Updated on: Wed, 03 May 2017 18:38]

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Re: Where can I find z-scores? [message #12374 is a reply to message #12341] Mon, 08 May 2017 07:07 Go to previous messageGo to next message
Gowokani is currently offline  Gowokani
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Dear Trevor,

I am trying to calculate the HAZ and WAZ for 1992, 2000, 2006. I understand that you say these can simply be dowloaded in a "seperate file" which is available. Is this downloadable file located where we download the other datasets for a sepcific coutnrty? I cannot fid this. And if so, how is it matched to the individual data for a child/ mother characteristics in the other files/

Gowo


Gowokani Chijere Chirwa
Re: Where can I find z-scores? [message #12378 is a reply to message #12374] Mon, 08 May 2017 10:35 Go to previous messageGo to next message
Trevor-DHS is currently offline  Trevor-DHS
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You didn't say which country you are interested in data for, but I'm guessing that you are looking for data for Malawi. If so, for example, you can go to the Malawi datasets download page for 1992, and find the files marked "Height and Weight Scores - WHO Child Growth Standards". These files contains the anthropometric z-scores. In the zip files for the height and weight scores you will find a document called merge.doc that describes how to merge the HW files to the other datasets.
Re: Where can I find z-scores? [message #12379 is a reply to message #12378] Mon, 08 May 2017 10:42 Go to previous messageGo to next message
Gowokani is currently offline  Gowokani
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Trevor

Many thanks, you are a star- so fats and helpful

Gowo


Gowokani Chijere Chirwa
Re: Where can I find z-scores? [message #12793 is a reply to message #91] Fri, 14 July 2017 06:34 Go to previous messageGo to next message
habt_lancs is currently offline  habt_lancs
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Dear Liz-DHS,

I a couple of questions:

I am working on Ghana DHS

1. So let say we open the children's recod of DHS Ghana 2008. In that you will see two variables as far as height/age standard deviation is concerned: hw5 and hw70. What is the difference between them?

2. If you open the 1988 data of DHS Ghana in the 'height and weight' file you see, for-instance, ht/a standard deviations (according to who) or hc70. is this variable constructed using the new WHO growth standard (haz2006) or does it follow a different standard? Or, are hw 70 and hc70 comparable (constructed with same WHO growth standard)

3. i see these variables are reported in 100s points (like -200, -100), should i divide them by 100 to get the standard deviation- the Z-score?

Best Regards,

Re: Where can I find z-scores? [message #12794 is a reply to message #130] Fri, 14 July 2017 06:40 Go to previous messageGo to next message
habt_lancs is currently offline  habt_lancs
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Dear Trevor,

The question is does the "Height and Weight Scores - WHO Child Growth Standards" file, say, in Ghana DHS 1988 constructed based on the new WHO growth standard? Can we merge it and compare it with like DHS 2008 height for age data?

best,
Re: Where can I find z-scores? [message #12797 is a reply to message #12794] Fri, 14 July 2017 11:30 Go to previous messageGo to next message
Trevor-DHS is currently offline  Trevor-DHS
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In 2006 WHO released new Child Growth Standards (http://www.who.int/childgrowth/en/). The anthropometric z-scores for these can be found in hc70 and hw70. Prior to 2006 we used the NCHS/CDC/WHO Growth reference and the z-scores for these can be found in hc5 and hw5.

The hc variables are part of the person's recode file for household members, and these provide the data for all children living in the household or who stayed in the household the previous night. The hw variables are restricted to children of interviewed women who were residents of the household or stayed in the household the previous night, and are a copy of the hc variables for that restricted subset.

The data are stored with 2 implied decimal places, and the values should be divided by 100 to restore the decimals. Howeveer, if you are just comparing to cut-offs such as -2 SD, then you can just write hc70 < -200 instead.

In DHS tabulations for nutritional status, we analyze the hc70 series variables.

The separate "Height and Weight Scores - WHO Child Growth Standards" are the z-scores for the new growth standard for older surveys and are design to be merged directly into the recode files, either with the KR file if the data were originally collected just for children of interviewed women (the earlier surveys), or with the PR file if te data were collected as part of the household questionnaire (later surveys).
Re: Where can I find z-scores? [message #12798 is a reply to message #12797] Fri, 14 July 2017 11:39 Go to previous messageGo to next message
habt_lancs is currently offline  habt_lancs
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Thanks so much; that helps a lot.
Re: Where can I find z-scores? [message #12801 is a reply to message #12797] Fri, 14 July 2017 12:28 Go to previous messageGo to next message
habt_lancs is currently offline  habt_lancs
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Dear Trevor,

I could not find household level information for Ghana DHS 1988. Variables like household head information and wealth.

any help?
Re: Where can I find z-scores? [message #12802 is a reply to message #12801] Fri, 14 July 2017 14:01 Go to previous messageGo to next message
Trevor-DHS is currently offline  Trevor-DHS
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These typically don't exist for the oldest surveys. The wealth index was not developed until the early 1990s and requires a good number of asset questions that were not asked in earlier surveys. Similarly, household and persons recode datasets do not exist for the DHS-I surveys, but you can find the household raw data and can construct some information about the head of household from that.
Re: Where can I find z-scores? [message #12803 is a reply to message #12802] Fri, 14 July 2017 14:11 Go to previous message
habt_lancs is currently offline  habt_lancs
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Thanks so much.
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