Dillon JJ
Fish oil for IGA nephropathy: efficacy and interstudy
variability
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1332 1996
The author has analyzed the outcome in 5 controlled trials of fish oil
in IgA nephropathy, reported between 1984 and 1994. Individual
outcomes of the studies were combined, using a random effects model
and effect size were weighted according to the number of
patients in the study, the length of follow up, and the number of
measurements of renal function. Two studies favored the use of fish
oil and three did not. The results were expressed as std. deviation, a
positive value indicating beneficial effects of the fish oil
treatment.
Although the combined result was +0.26 S.D., the value did not reach
statistical significance. The author concluded that the present
literature neither established nor excluded the beneficial effects of
fish oil.
Comment: Several issues come up when five trials are pooled
for meta analysis. One study did not contain sufficient data to judge
(Hamazaki T et al, Lancet, 1: 1017,1984). Another study was not
randomized and relied on patients' pretreatment profile of serum
creatinines as control values (Cheng IKP et al, Nephrol Dial
Transpl 5: 241, 1990). Three other studies were randomized and
prospective. Donadio's study had a large number of patients, a fairly
long duration of follow-up of 2 yrs, and showed a beneficial effect of
fish oil (N Engl J Med 331: 1194, 1994). Bennett et al found no
benefit from fish oil given for 2 yrs, but had fewer patients than the
Donadio study (Clin Nephrol 31:128, 1989). Pettersson and
others did not find any benefit from fish oil which was given only for 6
months (Clin Nephrol 41: 183, 1994). Longer duration of
treatment could have yielded different results.
In addition to differences in design, among the five reports there
were variations in the dose of fish oil, duration of treatment, and
levels of renal function at the time of entry into the study. Although
statistical adjustments were made for many of these differences, I
still have a problem pooling them for analysis because of basic
differences, for e.g., in their design. Additionally, there should be
significant differences in general management of patients over 10 yrs
of reporting and across four continents. At the moment, I employ the
Donadio strategy of treating with fish oil those patients who fall into
the entry criteria of that study.
(B.S. Kasinath, M.D., University of Texas at San Antonio)
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Am Soc Nephrol
Proteinuria/Hematuria :
IgA Nephropathy