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Using a variable in NIS database

Regular Contributor
Posts: 173

Using a variable in NIS database

Has anyone here used NIS database for analyses? which gives the information about numbers of discharges from each hospital.

I am trying to run a regression model and using a variable called TOTAL_DISC,

I want to use it to indicate the hospital volume in my analyses; but I am facing some issue with it. No matter what independent variables I include in my regression model along with this one, the results always shows as 1.00 as the value for point estimate and the LCL and UCL, as highlighted below. I am not sure why i am getting these results and cannot interpret the Odds ratio value and LCL/UCL for this variable.

Appreciate if anyone who has nay clue, could provide some guidance in this regard and advise if there is any other way to use this variable and get comprehensible result values or if there is anything I am doing incorrectly.

Below is the table, with the value highlighted..

EffectPoint Estimate95% Wald
Confidence Limits
FEMALE 1 vs 01.7841.7091.862
race1 2 vs 11.0951.0121.184
race1 3 vs 11.1511.0611.249
race1 4 vs 10.8750.7481.025
race1 5 vs 11.131.0251.246
ZIPINC_QRTL 2 vs 10.9850.9291.045
ZIPINC_QRTL 3 vs 11.0550.9941.119
ZIPINC_QRTL 4 vs 11.1981.1271.274
HOSP_LOCATION 0 vs 10.970.8821.067
H_CONTRL 2 vs 11.0780.9941.169
H_CONTRL 3 vs 10.8920.8090.983
HOSP_TEACH 1 vs 01.1081.0581.161
dm_all 1 vs 00.7910.7540.83
CM_HTN_C 1 vs 00.8370.80.875
morbidobesity 1 vs 00.9060.7961.031
hyperlipidemia 1 vs 00.8120.7780.848
CM_PERIVASC 1 vs 02.5542.4212.694
CHF 1 vs 02.1421.6362.804
Super Contributor
Posts: 543

Re: Using a variable in NIS database


From the HCUP website I see that total_disc takes uniform values  

VariableDescriptionValueValue Description
TOTAL_DISCTotal hospital discharges5(n)Total hospital discharges

What is the distribution of total_disc? Maybe in your sample you have exactly the same #s in each 'group' of total_disc (what I mean is that maybe there is an equal # of total_disc = 1, total_disc = on...).

Smiley Happy

Regular Contributor
Posts: 173

Re: Using a variable in NIS database

Thanks for your response!

No, they are not the uniform values.

Please take a look at the results of proc freq and proc univariate attached to the original post.

Let me know what you think.

Thanks much!

Super Contributor
Posts: 543

Re: Using a variable in NIS database

Ok, so giving the distribution of total_disc you have ~ 65% of the data with less than 100 discharges, but the max is 1522(discharges)

Ok, so if you look at the histogram of total_disc you notice that it is not only highly skewed, but it also has a high kurtosis.So, I wonder if you would categorize the total_disc into say 5 or 6 groups, like

0 to 25, 25 to 50, 50 to 75, 75 to 100, then > 100...or  100 to 125...and > 125

Anyway, my point it to sort of create groups such that any total_disc > some cutt-of point (between 100 and 200) gets lumped into one group.

Do you know what I mean?

Regular Contributor
Posts: 173

Re: Using a variable in NIS database

Hi Anca,

I see what you are saying, yes i would be a good idea to categorize them. But I am not sure where you see that 65% of the data is with <100 discharges and max is 1522. Where do you see those numbers? In fact what i see that 75% of the data shows discharges upto 27408.

Super Contributor
Posts: 543

Re: Using a variable in NIS database

sorry, I got my numbers confused. I was looking a the distribution of the frequencies of total_disc, which obviously is not the same as total_disc.

But you get my idea, so let me know if the ORs look better once you've grouped the variable.(possibly in quartiles,or quintiles)

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