Dear Paul,
I do not understand why you disregard published data more than 7 years old?
You are obviously critical of trials and appropriately examining trial
quality by looking for intention to treat analyses, concealed allocation and
adequate power. This is great!
However, to increase your suspicion purely due to the age of the trial's
publication date is an unhealthy bias. Why 7 years? Why not 6 or 5? And
are you accounting for the time taken to publish. Most trials take some
time to be published with Stern and Simes (1997) demonstrating, in an
interesting paper on publication bias, that the median time to publication
was 4.69 (3.75 to 5.72) years for clinical trials with significant results
and 7.99 (7.02 to never) years for clinical trials with null results. So if
a trial ran for 1 year, it is quite possible that the first participant was
enrolled already 4.75 years ago. This only gives your article a shelf life
of around 2 years and that's at best case scenario.
Also, if it was necessary to be suspicious of anything over 7 years old, we
would have to keep running the same trials every 7 years to re-establish
evidence or stop using the treatment. For example, a systematic review of 5
trials (Lumley 2004)concluded that taking folate while pregnant has a strong
protective effect against neural tube defects. Trial dates were 1981, 1991,
1992, 1994 and 1999. As only one of these makes your cut of 7 years, would
4 be treated as suspicious and therefore the use of folate to prevent
disorders such as spina bifida be questioned?
In regards to recent VAS reliability and validity studies, Bijur et al did a
reliability study in 2001 for the VAS in measurment of acute pain in
emergency departments. 96 participants were assessed and Intraclass
Correlation Coefficients were collectively 0.97 (95%CI = 0.96 to 0.98).
Kind regards,
Joel.
PS
Paul wrote:
>There is a significant difference between fact and reality!
Do you have a p value for this? ;)
Bijur PE, Silver W, Gallagher J: Reliability of the visual analog scale for
measurement of acute pain. Academic Emergency Medicine 8: 1153, 2001.
Lumley J, Watson L, Watson M, Bower C. Periconceptional supplementation with
folate and/or multivitamins for preventing neural tube defects (Cochrane
Review). In: The Cochrane Library, Issue 3, 2004. Chichester, UK: John Wiley
& Sons, Ltd.
Stern JM, Simes RJ: Publication bias: evidence of delayed publication in a
cohort study of clinical research projects. British Medical Journal 315:
640, 1997.
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