Identifying clinical factors associated with invasive pneumococcal disease in Taiwan

Dear Editor Invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae has been a notifiable disease in Taiwan since 2007. It results in either long-term problems, such as brain damage and hearing loss, or a particularly high case-fatality rate and economic burden.1, 2 Previous studies reported a variety of underlying medical conditions with increased susceptibility to IPD,3, 4 but large-scale indigenous studies regarding these risk factors are limited. We conducted a nationwide study in Taiwan utilizing the national health insurance research database (NHIRD) to identify gender and age-related risk factors that are associated with IPD. We used a subset of the database, Longitudinal Health Insurance Database (LHID) 2010 from NHIRD, to identify 903 IPD patients defined by International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) during 2000 to 2013 in Taiwan. The non-IPD group was matched with the IPD group according to age and gender of the person diagnosed with IPD at a ratio of 4:1. After matching, there were 900 patients in the IPD group and 3600 patients in the non-IPD group. We identified the potential IPD risk predictors4 prior to the index date of IPD diagnosis for those with more than two outpatient visits or at least one admission within 12 months, including cases for asthma, non-asthma chronic obstructive pulmonary disease (COPD), cardiac disease, cancer/ immunosuppression, chronic renal/hepatic disease, and diabetes mellitus. Multivariate logistic regression analyses were performed on the whole sample and subgroups. After adjustment for demographic characteristics, the factors of asthma (OR = 3.36, 95% CI = 1.88-6.01), non-asthma COPD (OR = 3.15, 95% CI = 2.51-3.96), cardiac disease (OR = 1.72, 95% CI = 1.32-2.23), cancer/immunosuppression (OR = 1.65, 95% CI = 1.21-2.26), chronic renal/hepatic disease (OR = 1.71, 95% CI = 1.33-2.21), and diabetes mellitus (OR = 1.52, 95% CI = 1.16-2.01) were found to be associated with an increased risk of IPD. For males, the factors of asthma, non-asthma COPD, cardiac disease, cancer/immunosuppression, and chronic renal/hepatic disease were related to increased risk of IPD. The factors including asthma, non-asthma COPD, and diabetes mellitus were found to spur increased risk of IPD in females. In terms of age, among children aged 0 to 4 years, only asthma was associated with the risk of IPD. In the age group 5 to 17 years, all risk factors were the least strongly related to IPD. Among those aged 18 to 64 years, most factors were related to increased risk of IPD except for cardiac disease. In the age group 65 years and over, the highest risk was among those with non-asthma COPD and cardiac disease (Table 1). In conclusion, our study has demonstrated that asthma, non-asthma COPD, cardiac disease, cancer/immunosuppression, chronic renal/hepatic disease, and diabetes mellitus were significantly associated with risk of IPD. Notably, asthma was an independent risk factor for IPD in children 0 to 4 years, while non-asthma COPD was a major risk factor for IPD in elders. Interestingly, no risk factors included in our study showed significant impacts on patients aged 5 to 17, which might be partly due to their mature innate and adaptive immune responses. Patients who have almost all the above-mentioned comorbidities are currently recommended for pneumococcal vaccination except those with asthma in Taiwan.5 Therefore, the importance of self-paid pneumococcal vaccination among asthmatic patients aged 18 to 65 without routine immunization should be emphasized. The authors are also grateful to Research Center of Medical Informatics, Kaohsiung Veterans General Hospital, for data management and statistical analysis. All authors declare no conflicts of interests.

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