[EpiData-list] Related files and conditional chk

epidata-list at lists.umanitoba.ca epidata-list at lists.umanitoba.ca
Wed Apr 28 10:57:51 CDT 2010

Hello epidata friends,

Im occasionally reading emails in the list about limitations in the related
rec files. The last I remember was about double entry, which I did not read
a proposition of solution. Here goes another problems that I could not solve

Im working with a dataset entry with two purposes: 1) to estimate a
trajectory of a particular liver enzyme over time while patients is under
therapy and 2) estimate the risk of liver toxicity while in therapy. The tow
objectives are time dependent.

In the first objective the possible result is a graph with a line conecting
dots which represents the enzyme values in each time point.

The second is a cox model or a exponential survival model which the outcome
is liver toxicity due to therapy. In this one, the medications may change
over time.

Therefore I was imagining creating a main recfile with clinical
characteristics of each patient that are permanent, that is, do not change
over time such as HIV serology status, and create tow related recfiles with
1) data about each liver panel with correspondent date and 2) the medication
in use with initial date and end date with the end status (cure, default,
death etc); both may be fed with several data from different dates for each

Now ... one common problem with dates is that very often typing mistakes
make dates incompatible such as:

1) the second liver panel was collected BEFORE the first.

2) The end of medication was registered BEFORE the beginning or the second
medication started BEFORE the end of the first.

To control this sort of mistake is easy with conditional checking when the
dates are in the same recfile. But if I make related files the conditional
checking with dates should be done in the same field  (or different fields)
in different records. That is ... I should ask epidata to go in other record
with the same key (ID) and check if the collection date is before or after
the date of this open record.

The question is ... is this possible? Does anyone have a sugestion to
workaround (possibly having all the dates in the main recfile and related

An example:

******** Main qesfile

ID ####
name _____
hiv #
start <dd/mm/yyyy>
end <dd/mm/yyyy>
toxicity #

******* First related file - liver panel

ID ####
coldate <dd/mm/yyyy>
panelnum #
alt ####
ast ####

****** Secodn related file - medication

ID ####
TBdrugs _______
HIVdrugs _______
combstart <dd/mm/yyyy>
combend <dd/mm/yyyy>
outcome #

Kind regards,

Abraço forte e que a força esteja com você,

Dr. Pedro Emmanuel A. A. do Brasil
Instituto de Pesquisa Clínica Evandro Chagas
Fundação Oswaldo Cruz
Rio de Janeiro - Brasil
Av. Brasil 4365
Tel 55 21 3865-9648
email: pedro.brasil at ipec.fiocruz.br
email: emmanuel.brasil at gmail.com

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www.epidata.dk - entrada de dados.
www.r-project.org - análise de dados.
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