The risk of acute rheumatic fever (ARF) and acute post streptococcal glomerulonephritis (APSGN) following streptococcal infection is still poorly quantified. While the elevated risk of ARF following group A streptococcus (GAS) pharyngitis appears certain, there are many unresolved questions, including the timing of this elevated risk; the relative importance of Group C/G infections; and the role of skin infections versus pharyngeal infections in initiating ARF and APSGN.
This study takes advantage of New Zealand's linked health data to investigate these relationships using two large patient datasets: Hospitalisation data for 2000-15 for a wide range of conditions, including pharyngitis and skin infections and laboratory test data for 2010-16 for throat and skin swabs that are positive and negative for GAS and Group C/G detections. These exposure data are then individually linked, via an encrypted patient number, to initial ARF and APSGN case data to detect these subsequent events and estimate rates and rate ratios.
Preliminary analysis shows a strong positive relationship between having a GAS positive throat swab and the risk of ARF over the following 8-90 days (RR 5.53, 95%CI 3.96-7.72). There is no significant rise in risk during this same time-period following Group C/G positive isolates (RR 1.31, 95%CI 0.57-3.01).
Hospitalisation data show an increased risk of ARF and APSGN in the 90 days following hospitalisation for acute upper respiratory tract infection. The association with skin infection hospitalisations is equivocal. Comprehensive results will be presented at the meeting.