Recorded gonorrhoea rates in Denmark, 1900–2010: the impact of clinical testing activity and laboratory diagnostic procedures

OBJECTIVES: Assessment of the relations between recorded gonorrhoea rates and clinical testing activity and disposable diagnostic tests. METHODS: In Denmark, two sources of information on the epidemiology of gonorrhoea are available: (1) a mandatory clinical notification system (since 1867) comprising summary information about geographic distribution, season, age group and gender; in 1994, more detailed anonymous individualised epidemiological information was included; (2) a voluntary countrywide laboratory surveillance system for culture-confirmed cases (since 1957) comprising information about patient's age and gender, infected anatomical sites and medical setting attended. RESULTS: Both surveillance systems showed marked simultaneous changes in gonorrhoea rates, although periodically considerable under-reporting or under-diagnosing was demonstrated. The annual incidence of notified cases peaked in 1919 (474/100 000), in 1944 (583/100 000) and in 1972 (344/100 000). Since 1995, the incidence has been at a low endemic level (1.5–10/100 000) and the total male/female incidence ratios were from 3 to 7 times higher than previously recorded. Among approximately 2 million persons tested during 1974–1988 78 213 men and 63 143 women with culture-confirmed gonorrhoea were identified. During this period, pharyngeal sampling was performed in 36% of men and 25% of women with gonorrhoea; pharyngeal gonorrhoea was found in 10% and 16%, respectively; 40% and 30% of these patients had no concomitant urogenital gonorrhoea. Among men with gonorrhoea, 34% were sampled from the rectum; 9% had rectal gonorrhoea, among whom the rectum was the only infected site in 67%. CONCLUSIONS: Crucial factors for case finding are clinical sampling tradition and appropriate laboratory diagnostic facilities. When case finding is insufficient, a reservoir of asymptomatic rectal or pharyngeal gonorrhoea remains unrecognised.