topic Re: Equation in SAS in SAS Programming

Equation in SAS

ursula — Sat, 17 Sep 2022 04:43:53 GMT

Hi,

is anybody able to help me of how to write the following equation in SAS?

eGFR_cr = 142 x min(S_cr/κ, 1)^α x max(S_cr/κ, 1)^-1.200 x 0.9938^Age x 1.012 [if female]

where:

S_cr = standardized serum creatinine in mg/dL

κ = 0.7 (females) or 0.9 (males)

α = -0.241 (female) or -0.302 (male)

min(S_cr/κ, 1) is the minimum of S_cr/κ or 1.0

max(S_cr/κ, 1) is the maximum of S_cr/κ or 1.0

Age (years)

Thanks in advance!

Re: Equation in SAS

FreelanceReinh — Sat, 17 Sep 2022 09:32:03 GMT

Hi @ursula,

With input data like this

data have;
input SCr age sex $;
cards;
0.82 65 M
0.93 71 F
;

you can compute eGFR according to your formula as follows

data want;
set have;
if n(SCr, age)=2 then do;
       if sex='F' then eGFR=142*min(SCr/0.7,1)**-0.241*max(SCr/0.7,1)**-1.2*0.9938**age*1.012;
  else if sex='M' then eGFR=142*min(SCr/0.9,1)**-0.302*max(SCr/0.9,1)**-1.2*0.9938**age;
end;
run;

and, if you like to get external confirmation, compare a few results to those of the online calculator https://www.kidney.org/professionals/kdoqi/gfr_calculator with

Serum Cystatin C: left blank
Standardized Assays: Yes
Adjust for body surface area: No

Re: Equation in SAS

ursula — Sat, 17 Sep 2022 18:22:09 GMT

Thank you so much for your help!

I really appreciate for the prompt response!

Have a great weekend!

Re: Equation in SAS

ursula — Sat, 17 Sep 2022 18:44:19 GMT

sorry , I have a tiny quick question about the code from you.

data want; set have; if n(SCr, age)=2 then do; if sex='F' then eGFR=142*min(SCr/0.7,1)**-0.241*max(SCr/0.7,1)**-1.2*0.9938**age*1.012; else if sex='M' then eGFR=142*min(SCr/0.9,1)**-0.302*max(SCr/0.9,1)**-1.2*0.9938**age; end; run;

what does the "n" ( if n(SCr, age) = 2 then do:) mean?

Thanks,

Re: Equation in SAS

Kurt_Bremser — Sat, 17 Sep 2022 19:21:04 GMT

Study the documentation of the N Function
https://documentation.sas.com/doc/de/pgmsascdc/9.4_3.5/lefunctionsref/n0h1d8gxwr1ml7n1qdt35v3i6u7r.htm

Re: Equation in SAS

ursula — Sat, 17 Sep 2022 19:31:53 GMT

Thanks much! got it now !