The capture–recapture method was used to estimate the sensitivity
of case finding in two
national STD surveillance systems: (1) STD registration at municipal health
services (STD-MHS);
(2) statutory notification by clinicians (NNS). To identify those cases
common to both
surveillance systems, cases from 1995 were compared using individual identifiers.
Estimated
sensitivities for syphilis were: STD-MHS 31% (95% CI: 27–35%), NNS
64% (56–71%); and
for gonorrhoea: STD-MHS 15% (14–18%), NNS 22% (19–25%). The
combined sensitivity of
both systems was 76% for syphilis and 34% for gonorrhoea. Differences in
the sensitivity of
the systems were significant. The NNS was more sensitive than the STD-MHS,
and the
identification of cases was significantly more sensitive for syphilis than
for gonorrhoea. A
stratified analysis showed comparable results for the two sexes. Knowledge
on the sensitivity of
surveillance systems is useful for public health decisions and essential
for international
comparisons.