Fjölrit RALA - 22.03.1979, Page 95

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412 Morbus cordis ischemicus chronicus
413 Angina rectoris
414 Morbus cordis ischemicus asymtomaticus
Investigations in other countries have shown that these
two classifications are not comparable (1,2). In the U.S.A.,
for example, it is necessary to add 14.6% to No. 420 (7th) to
make it comparable to No. 410-414 (8th). This difference is
due to diagnostic habits or fashions of doctors and may vary
between countries. A systematic comparison of the 7th and 8th
ICD classifications in Iceland has not been done. In order to
estimate this factor, the two nearest diagnostic categories to
coronary artery disease were also investigated, that is,
(A) Myocardial degeneration No. 422 in the 6th and 7th ICD
editions but No. 428 in the 8th, (B) Hypertensive heart di-
sease which is No. 440-443 in the 6th and 7th editions but
No. 402 and 404 in the 8th.
Methods of calculations:
The death rate per 100,000 inhabitants was calculated for
10 year age groups for coronary artery disease and for myocar-
dial degeneration plus coronary artery disease. For other di-
agnostic categories the numbers were so small that the death
rate was only calculated for age group 25 and over.
In order to equal out random variation between years, a
three year running mean was used. Changes were then calculated
as a percentage of the first running mean. For coronary artery
disease plus myocardial degeneration, the mean death rate for
the period 1951-55 was used. For the categories, the mean for
the period 1955-57 was used.
Results
In figure 1 the percentage of death certificates based on
doctors examination and autopsy for 4 periods is shown. The
autopsy rate is lowest 1951 - 13% - but highest 1966-70 - 39% -
and decreases to 30% 1971-74. Certificates based on döctors'
examination before and after death were most common 1951 and
1960 or 58% and 59% but decreased to 40% in 1966-70. The qual-
ity of death certificates is therefore lowest in 1951 and equal
and highest in 1060-70, but decreases again 1971-74.