Low Rates of Transfusion Transmitted Infection Screening in Chronically Transfused Adults with Sickle Cell Disease

INTRODUCTION: Adults with Sickle Cell Disease (SCD) treated with chronic transfusions usually receive 2 to 10 units of packed red blood cells (pRBCs) every three to five weeks, as either simple or exchange transfusions. In the USA, the routine screening of blood products by nucleic acid amplification tests (NAT) has reduced the risk of transmission of HIV, hepatitis C (HCV) and hepatitis B (HBV) per unit of pRBC to 1 in 1.5, 1.1, and 1 million respectively. Although rates of transfusion transmitted infections (TTI) in the general population are low, chronically transfused SCD patients may be at an increased risk of TTIs because of their many lifetime transfusions. The 2014 National Heart, Lung and Blood Institute (NHLBI) guidelines recommend annual screening for HIV, HBV, and HCV in chronically transfused SCD patients. The purpose of this single-center study was to (1) determine the adherence to this recommendation over 5 years and (2) assess HBV immunity and HBV vaccination rates.

METHODS: We included chronically transfused SCD patients at the Johns Hopkins Sickle Cell Center for Adults with 12 or more months of chronic transfusion treated between October 2014 and September 2019, designated as Year 1 (Y1) to Year 5 (Y5). A systematic chart review assessed the status of screening for TTIs using standard tests for HIV, HCV, and HBV infections and for HBV immunity. Vaccination data were collected from multiple sources including, the electronic medical records which are imported from the Maryland’s Immunization Information System, primary care providers (PCPs), and study subjects.

RESULTS: The study included 93 subjects with a median age of 34 years (range 29-43); 48% were male. Thirteen subjects (13.9%) received partial manual exchanges, and 80 (86%) received automated exchange transfusions. The number of subjects receiving chronic transfusions increased in each study year, with 52 subjects in Y1 and 93 subjects in Y4 subsequently followed up through study Y5, constituting 361 person-years. The median number of units transfused per person per month was 4 (IQR 2.2 – 5.7); 29 subjects (31.2%) received fewer than 25 units, 56 subjects (60.2%) received 25-100 units and 8 subjects (8.6%) received greater than 100 units per year on average. No subjects were screened annually for TTI. The TTI screening rates for HIV, HCV and HBV were 0.53, 0.35 and 0.30 per person-year of transfusion. In the 5-year study period, 74 subjects (79.6%) were screened for HIV, 65 subjects (69.9%) for HCV and 58 subjects (62.4%) for HBV infections at least once. Screening identified no new HIV or HBV infections Two new HCV infections were diagnosed, but for one subject, RNA PCR for HCV was negative. The mode of transmission of the HCV infections was unclear. Nineteen (20.4%) subjects had documentation of HBV vaccination, with a non-significant trend towards younger age among patients with evidence of HBV vaccination compared to those without (Median 29(IQR 25-36) vs 36(IQR 30-43) years, p=0.13). Among the subjects with incomplete vaccination records, the PCPs and subjects did not have additional vaccination information. Among the 57 subjects tested for anti-HBs antibody titres, 47.4% had non protective titres.

CONCLUSIONS: At our center, adherence to the NHLBI TTI screening guidelines was low; the lowest screening rates were for HBV. Of the TTIs evaluated, new cases of HCV were detected in our study population, indicating a need for regular screening for this virus. A larger sample may be needed to evaluate the need for annual screening. We also noted poor documentation of HBV immunization and lower rates of immunity against HBV suggesting the need for an improved vaccination strategy and an evaluation of the possible immunological reasons behind the same.