Accuracy of Blood Transfusion Records in a Population-based Perinatal Data Registry

Accuracy of postpartum hemorrhage coding in the Swedish Pregnancy Register

INTRODUCTION

Postpartum hemorrhage (PPH) is recognized as a leading cause of obstetric morbidity and mortality. Population-wide studies have used International Classification of Diseases (ICD) diagnostic codes to track and report the prevalence of PPH. Although the 10th revision (ICD-10) was introduced in Sweden in 1997, the accuracy of ICD-10 codes for PPH is not known. Thus, the aim was to determine the accuracy of diagnostic coding for PPH in the Swedish Pregnancy Register.

MATERIAL AND METHODS

We performed a retrospective cohort study of 609 807 deliveries in Sweden between 2014 and 2019. Information on ICD-10 codes for PPH and estimated blood loss were extracted from the Swedish Pregnancy Register. Using an estimated blood loss >1000 mL as the reference standard, we evaluated the diagnostic accuracy of ICD-10 codes for PPH by estimating sensitivity, specificity, positive predictive value and negative predictive value with exact binomial 95% confidence intervals (CIs). In our secondary analysis, we assessed the ICD-10 coding accuracy for severe PPH, defined as an estimated blood loss >1000 mL and transfusion of at least 1 unit of red blood cells registered in the Scandinavian Donations and Transfusion database.

RESULTS

Of the 609 807 deliveries, 43 312 (7.1%) had an ICD-10 code for PPH and 45 071 (7.4%) had an estimated blood loss >1000 mL. The ICD codes had a sensitivity of 88.5% (95% CI 88.2-88.7), specificity of 99.4% (95% CI 99.4-99.4), positive predictive value of 92.0% (95% CI 91.8-92.3) and negative predictive value of 99.1% (95% CI 99.1-99.1). In our secondary analysis, on deliveries with severe PPH, the sensitivity for an ICD code was 91.3% (95% CI 90.7-91.9), whereas specificity was 83.5% (95% CI 82.3-84.6).

CONCLUSIONS

Our findings indicate that ICD-10 codes for PPH in Sweden have moderately high sensitivity and excellent specificity. These results suggest that PPH diagnostic codes in medical records and linked pregnancy and birth registers can be used for research, quality improvement and reporting PPH prevalence in Sweden.

Inter-hospital variation in use of obstetrical blood transfusion: a population-based cohort study

OBJECTIVE

To identify the extent of hospital-to-hospital variation in use of obstetrical blood transfusion.

DESIGN

Population-based cohort study linking provincial perinatal and blood transfusion registries.

SETTING

British Columbia, Canada, 2004-2015.

POPULATION

All pregnant women delivering at or beyond 20 weeks' gestation at any British Columbia hospital.

METHODS

Mixed-effects regression models were used to estimate hospital-specific transfusion rates after sequentially accounting for (1) the role of random variation, (2) maternal medical and obstetrical characteristics (i.e. patient case mix) and (3) institutional and delivery factors (such as use of instrumental or caesarean delivery).

MAIN OUTCOME MEASURES

Hospital-specific use of obstetrical red blood cell transfusion.

RESULTS

Among 44 hospitals, crude institutional transfusion rates across the study period ranged from 3.7 to 23.6 per 1000, with an average of 8.3 per 1000. After adjusting for maternal characteristics, institution and delivery risk factors, a nearly three-fold difference in rates between the 10th and 90th percentile remained (5.4-14.5 per 1000). Twelve sites had rates significantly higher or lower than the provincial average. Women residing in remote areas were 2.5-fold (95% CI 1.8-3.5] more likely to receive a blood transfusion than were women residing in metropolitan areas.

CONCLUSIONS

Meaningful variation between hospitals in use of blood transfusion during pregnancy was not explained by differences in patient case-mix or institutional factors, suggesting that over- or under-utilisation of this resource may be occurring in obstetrical care.

TWEETABLE ABSTRACT

Use of blood transfusion in pregnant women varied broadly between hospitals in British Columbia, Canada.