Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
st: SKIN PRICK TEST ANALYSIS
"Cornelius Nattey" <email@example.com>
st: SKIN PRICK TEST ANALYSIS
Fri, 3 Jun 2011 11:14:38 +0200
I am involve in a study "Longitudinal variability of skin prick test results to six common aeroallergens (CA) and three soybean allergens"
The dependant variable is "changed status to CA" YES or NO. I.e. started off negative and became positive at some point in the survey to at least one CA or started off positive and became negative at some point in the survey to at least one CA = changes status YES; and if stayed the same throughout( ie negative negative or positive positive)
independent variables are: (1) the number of positive SPTs to CA at the initial test; (2) the size of the largest wheal at the initial test; and (3) the number of testings done.
What type of analysis can one do with this type of dataset?
Below are some considerations so please advice on what to do with the datasets:
The dataset with 110 people with 2 testings. At the initial testing we have +ve or -ve. At the second testing we have remained +ve, remained -ve, converted (-ve to +ve) or reverted. (1) We will examine determinants of conversion. But only people who were initially negative can convert. Does this mean that we drop from this analysis the subjects who were initially positive (they have no chance of getting the outcome conversion)?
I think we do not have to drop them as they still have the range of measurements across the independent variables and so can be used as a reference group for these variables. But I ask this question because for example in a study of the determinants of prostate cancer you would not include subjects who have had a prostatectomy (for non-cancer reasons). (2) Same consideration for the analysis of reversion.
The dataset with 4 testings does not have the same problem because conversion and reversion can occur along the time course of the study irrespective of initial status, and so all subjects are at risk of the outcome at some point (e.g. initially positive can revert and then convert so even if you are initially positive you have a risk of conversion at some point). I think.
Medical Scientist: Epidemiology and Surveillance
National Health Laboratory Service
National Institute for Occupational Health
Office: 011 712 6438
Fax: 086 604 1214
Cell: 079 631 5857
The views expressed in this email are, unless otherwise stated, those of the author and not those of the National Health Laboratory Services or its management. The information in this e-mail is confidential and is intended solely for the addressee.
Access to this e-mail by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted in reliance on this, is prohibited and may be unlawful.
Whilst all reasonable steps are taken to ensure the accuracy and integrity of information and data transmitted electronically and to preserve the confidentiality thereof, no liability or responsibility whatsoever is accepted if information or data is, for whatever reason, corrupted or does not reach its intended destination.
* For searches and help try: