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Dear Sir,
In their continuous anxious and compelling search of faults in published
research, Davey Smith and Egger's latest critical exercise (2 January,
p.56) falls short of being accurate. In their reference to a published
meta-analysis of observational data(1)and the re-analysis that
followed(2), they commit two sins. The first is to misquote the original
paper and the second, more important, is not to cross-check the facts.
They quote that "Cappuccio et al argued that this could be expected …".
Nowhere in the original manuscript is there such a statement. This
interpretation has been carefully construed from the paragraph discussing
potential sources of heterogeneity where the authors conclude that "…it
seems more likely that other characteristics, either not measured or not
considered in the analysis, may explain the differences across studies".
"Correcting the meta-analysis for this error (and several other
mistakes)…" they then go plotting Birkett's estimates in the figure.
However, they have conveniently ignored our correspondence to Birkett's
publication(3)where we clearly challenged some of Birkett's calculations.
Davey Smith and Egger's letter seems to crucify human error as misleading
meta-analysis without realising that whilst the inaccuracies discussed
(and in part ackowledged(3)) have led to minor changes in the overall
estimate of effect (the relevance of which is minimal and openly discussed
in view of the results of controlled trials(4)), their letter intends to
mislead by the use of misquotes and inaccuracies those readers who are
unlikely to go and read the original publications.
Yours sincerely
Francesco P Cappuccio
Reader in Preventive Cardiovascular Medicine
Department of Medicine
St George's Hospital Medical School, London SW17 0RE
References
1)Cappuccio FP, Elliott P, Allender PS, Pryer J, Follman DA, Cutler
JA. Epidemiologic association between dietary calcium intake and blood
pressure: a meta-analysis of published data. Am J Epidemiol 1995; 142:
935-945
2)Birkett NJ. Comments on a meta-analysis of the relation between
dietary calcium intake and blood pressure. Am J Epidemiol 1998; 148: 223-
228
3)Cappuccio FP, Elliott P, Follmann D, Cutler JA. Authors' response
to "Comments on a meta-analysis of the relation between dietary calcium
intake and blood pressure". Am J Epidemiol 1998; 148: 232-233
4)Cappuccio FP. The "Calcium antihypertension theory". Am J Hypertens
1999; 12: in press.
Misleading inaccuracies do more harm than good
Dear Sir,
In their continuous anxious and compelling search of faults in published
research, Davey Smith and Egger's latest critical exercise (2 January,
p.56) falls short of being accurate. In their reference to a published
meta-analysis of observational data(1)and the re-analysis that
followed(2), they commit two sins. The first is to misquote the original
paper and the second, more important, is not to cross-check the facts.
They quote that "Cappuccio et al argued that this could be expected …".
Nowhere in the original manuscript is there such a statement. This
interpretation has been carefully construed from the paragraph discussing
potential sources of heterogeneity where the authors conclude that "…it
seems more likely that other characteristics, either not measured or not
considered in the analysis, may explain the differences across studies".
"Correcting the meta-analysis for this error (and several other
mistakes)…" they then go plotting Birkett's estimates in the figure.
However, they have conveniently ignored our correspondence to Birkett's
publication(3)where we clearly challenged some of Birkett's calculations.
Davey Smith and Egger's letter seems to crucify human error as misleading
meta-analysis without realising that whilst the inaccuracies discussed
(and in part ackowledged(3)) have led to minor changes in the overall
estimate of effect (the relevance of which is minimal and openly discussed
in view of the results of controlled trials(4)), their letter intends to
mislead by the use of misquotes and inaccuracies those readers who are
unlikely to go and read the original publications.
Yours sincerely
Francesco P Cappuccio
Reader in Preventive Cardiovascular Medicine
Department of Medicine
St George's Hospital Medical School, London SW17 0RE
References
1)Cappuccio FP, Elliott P, Allender PS, Pryer J, Follman DA, Cutler
JA. Epidemiologic association between dietary calcium intake and blood
pressure: a meta-analysis of published data. Am J Epidemiol 1995; 142:
935-945
2)Birkett NJ. Comments on a meta-analysis of the relation between
dietary calcium intake and blood pressure. Am J Epidemiol 1998; 148: 223-
228
3)Cappuccio FP, Elliott P, Follmann D, Cutler JA. Authors' response
to "Comments on a meta-analysis of the relation between dietary calcium
intake and blood pressure". Am J Epidemiol 1998; 148: 232-233
4)Cappuccio FP. The "Calcium antihypertension theory". Am J Hypertens
1999; 12: in press.
Competing interests: No competing interests