Hospitalisation with injection‐related infections: Validation of diagnostic codes to monitor admission trends at a tertiary care hospital in Melbourne, Australia

Abstract

Introduction. Injection-related infections (IRI) cause morbidity and mortality in people who inject drugs. Hospital administrative datasets can be used to describe hospitalisation trends, but there are no validated algorithms to identify injecting drug use and IRIs. We aimed to validate International Classification of Diseases (ICD) codes to identify admissions with IRIs and use these codes to describe IRIs within our hospital. Methods. We developed a candidate set of ICD codes to identify current injecting drug use and IRI and extracted admissions satisfying both criteria. We then used manual chart review data from 1 January 2017 to 30 April 2019 to evaluate the performance of these codes and refine our algorithm by selecting codes with a high-positive predictive value (PPV). We used the refined algorithm to describe trends and outcomes of people who inject drugs with an IRI at Alfred Hospital, Melbourne from 2008 to 2020. Results. Current injecting drug use was best predicted by opioid-related disorders (F11), 80% (95% confidence interval [CI] 74-85%), and other stimulant-related disorders (F15), 82% (95% CI 70-90%). All PPVs were ≥67% to identify specific IRIs, and ≥84% for identifying any IRI. Using these codes over 12 years, IRIs increased from 138 to 249 per 100 000 admissions, and skin and soft tissues infections (SSTI) were the most common (797/1751, 46%). Discussion and Conclusion. Validated ICD-based algorithms can inform passive surveillance systems. Strategies to reduce hospitalisation with IRIs should be supported by early intervention and prevention, particularly for SSTIs which may represent delayed access to care.

Prevalence and incidence of emergency department presentations and hospital separations with injecting-related infections in a longitudinal cohort of people who inject drugs

“…ED presentations and hospital separations with an IRI were the outcomes, identified using ICD-10-AM codes in the Victorian Emergency Minimum Dataset and Victorian Admitted Episode Dataset. The ICD-10-AM codes were selected based on a previous study of IRIs in the same setting (Supplementary Table S1) and were identified as ED presentation or hospital separations with any IRI coded (i.e., either as a primary or secondary diagnostic code) [ 13 ]. In Australia, dedicated hospital staff are trained to retrospectively review clinical notes and encode ICD-10-AM data according to strict criteria for the Victorian Admitted Episode Dataset.…”

“…Hospitalization data, typically coded using International Classification of Diseases (ICD) codes, can be used to ascertain the incidence of IRIs requiring clinical care that are likely related to injecting drug use [ 12 ]. In Australia, incidence estimates of hospital separations with an IRI are limited to a cohort of people with a history of opioid agonist treatment in New South Wales (43 per 1,000 person-years between 2001 to 2017) and a cohort identified by an algorithm of ICD, Tenth Revision, Australian Modification (ICD-10-AM) codes at a Melbourne health service (192 per 100,000 annual hospital admissions between 2008 and 2018) [ 12 , 13 ]. International incidence estimates of hospital separations with an IRI are also limited to a cohort of people who injected heroin entering community-based substance use treatment in South London (73 per 1,000 person-years between 2006 and 2017) [ 11 ] and people who inject drugs with problematic alcohol use in a Swedish Prison and Probation Service (SSTI, 28.3 per 1,000 person-years and systemic bacterial infection, 9.1 per 1,000 person-years between 2001 and 2014) [ 15 ].…”

Epidemiology of acute infections in people who inject drugs in Australia

“…Colledge‐Frisby et al found that amongst participants accessing OAT in New South Wales between 2001 and 2017, the age‐adjusted incidence rate of hospitalisation for injecting‐related diseases increased from 34.8 to 54.9 per 1000 person years [ 29 ]. A recent Melbourne analysis at a tertiary hospital using International Classification of Diseases codes found that over 12 years between 2008 and 2020, acute infections increased from 138 to 249 per 100,000 admissions [ 34 ]. The burden of admissions was driven by SSTI, which accounted for nearly half of all admissions for people who inject drugs with acute infections (797/1751 = 46%) [ 34 ].…”

“…A recent Melbourne analysis at a tertiary hospital using International Classification of Diseases codes found that over 12 years between 2008 and 2020, acute infections increased from 138 to 249 per 100,000 admissions [ 34 ]. The burden of admissions was driven by SSTI, which accounted for nearly half of all admissions for people who inject drugs with acute infections (797/1751 = 46%) [ 34 ]. The majority of SSTI (86.5%, 689/797) were uncomplicated [ 34 ] and thus indicate a potential opportunity for improved early intervention and treatment to prevent hospitalisation.…”

“…The burden of admissions was driven by SSTI, which accounted for nearly half of all admissions for people who inject drugs with acute infections (797/1751 = 46%) [ 34 ]. The majority of SSTI (86.5%, 689/797) were uncomplicated [ 34 ] and thus indicate a potential opportunity for improved early intervention and treatment to prevent hospitalisation. Globally, there has been a dramatic rise in the cases of IE related to injecting drug use in the past 10 years, and it is estimated that people who inject drugs now comprise 8–38% of all cases of IE [ 35 , 36 , 37 ].…”