From the Department of Medical Epidemiology and Biostatistics, Karolinska Institute.
Section of Clinical Bacteriology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
Sex Transm Dis. 2021 May 1;48(5):329-334. doi: 10.1097/OLQ.0000000000001318.
We investigated the notification trends of sexually acquired chlamydia (chlamydia) and its association with testing in Sweden before (1992-2004) and after (2009-2018) the discovery of a new variant of Chlamydia trachomatis (nvCT).
We applied monthly time series analysis to study chlamydia trends and annual time series to study chlamydia rates adjusted for testing. We analyzed incidence nationally and by county group (based on able and unable to detect nvCT at time of discovery).
We present data on 606,000 cases of chlamydia and 9.9 million persons tested. We found a U-shaped chlamydia trend during the period 1992-2004, with an overall increase of 83.7% from 1996 onward. The period 2009-2018 began with a stable trend at a high incidence level followed by a decrease of 19.7% during the period 2015-2018. Peaks were seen in autumn and through during winter and summer. Similar results were observed by groups of county, although with varying levels of increase and decrease in both periods. Furthermore, increased testing volume was associated with increased chlamydia rates during the first period (P = 0.019) but not the second period.
Our results showed that chlamydia trends during the period 2009-2018 were not driven by testing, as they were during the period 1992-2004. This suggests less biased notified chlamydia rates and thus possibly a true decrease in chlamydia incidence rates. It is important to adjust case rates for testing intensity, and future research should target other potential factors influencing chlamydia rates.
我们研究了瑞典在发现沙眼衣原体（chlamydia）新变体（nvCT）之前（1992-2004 年）和之后（2009-2018 年）性传播衣原体（chlamydia）的通知趋势及其与检测的关联。
我们应用月度时间序列分析来研究衣原体趋势，并应用年度时间序列来研究调整检测后的衣原体率。我们在全国范围内和根据发现时能否检测到 nvCT 的能力进行分组的县组（基于发现时能否检测到 nvCT 的能力进行分组）分析发病率。
我们提供了 606000 例衣原体病例和 990 万人接受检测的相关数据。我们发现 1992-2004 年期间衣原体趋势呈 U 形，自 1996 年以来总体增加了 83.7%。2009-2018 年期间，一开始处于高发病率水平的稳定趋势，随后在 2015-2018 年期间下降了 19.7%。高峰期出现在秋季和整个冬季和夏季。虽然在两个时期都有不同程度的增加和减少，但县组观察到了相似的结果。此外，在第一个时期，检测量的增加与衣原体率的增加相关（P = 0.019），但在第二个时期则不然。
我们的结果表明，2009-2018 年期间衣原体趋势不是由检测驱动的，而在 1992-2004 年期间则是由检测驱动的。这表明通知的衣原体率偏差较小，因此可能真实的衣原体发病率下降。调整检测强度的病例率非常重要，未来的研究应该针对影响衣原体率的其他潜在因素。
