Background: The use of bacterial multiplex polymerase chain reaction (PCR) in children with suspected pertussis sometimes yields unexpected positive results for Mycoplasma pneumoniae. We aimed to evaluate the clinical significance of positive M. pneumoniae results in this population.
Methods: Retrospective cohort of consecutive patients with suspected pertussis tested with a bacterial multiplex PCR (including Bordetella pertussis and M. pneumoniae) between June 2015 and March 2017. Medical records were reviewed to compare demographics, clinical presentations and outcomes of patients positive for M. pneumoniae with those positive for B. pertussis and those with negative results, using multivariable logistic regression.
Results: A total of 1244 patients were included as follows: 56 (4.5%) with M. pneumoniae, 116 (9.3%) with B. pertussis and 1029 (82.7%) with negative results. Mean age was respectively 4.8 years, 6.5 years and 2.8 years (P < 0.05). Children with M. pneumoniae were less likely to present with cardinal symptoms of pertussis such as paroxysmal cough [adjusted odds ratio (OR): 0.19, 95% confidence interval (CI): 0.08-0.40) but were more likely to have fever (adjusted OR: 10.53, 95% CI: 3.54-39.49) and other nonspecific respiratory symptoms compared with children with B. pertussis. Children with M. pneumoniae had very similar clinical presentations to those with a negative PCR, but were more likely to have radiologically confirmed pneumonia (adjusted OR: 5.48, 95% CI: 2.96-9.99) and were less likely to be diagnosed with a concomitant viral infection (adjusted OR: 0.32, 95% CI: 0.07-0.99).
Conclusions: In children with suspected pertussis, the detection of M. pneumoniae is clinically relevant. However, the impact of this finding on patients' outcome is still unclear.