The implementation of effective blood donation screening for hepatitis B virus (HBV) anti-core antibodies with highly sensitive molecular HBV DNA detection in low-endemic countries like the United Kingdom has improved blood safety. However, the linkage to care and management for blood donors with occult HBV infection (OBI) is a complex dilemma involving virological, clinical, methodological, and social issues. Limited evidence suggests that OBI may accelerate the progression of liver disease and cancer. The need for a specialist referral for donors identified with OBI carries mixed opinions from blood establishments, hepatologists, and public health. Following extensive multidisciplinary discussions, experts agree upon a need for clear messaging for donors and to consider the oncogenic implications of OBI. Proposals for future studies are identified, and the applicability of the recommendations in low-resource, high-endemic regions is considered, as well as the inclusion of OBI in global hepatitis elimination targets.

BACKGROUND:Lookback investigations are conducted by blood services when a risk of transmission of infection from a donor to a recipient has been identified. They involve tracing transfusion recipients and offering them testing for the relevant infectious agent. Results are relayed to the recipient to provide reassurance that there has been no transmission or to ensure appropriate treatment and care if required, and blood services are able to learn lessons from the planning, delivery, and outcomes of the investigation. A national lookback exercise was conducted in Scotland following the introduction of a test to identify occult hepatitis B infection, as recommended by the UK Advisory Committee for the Safety of Blood, Tissues and Organs (SaBTO) in 2021. METHODS AND MATERIALS:This paper outlines the development and delivery of a national lookback program. It discusses the logistical, economic, ethical, regulatory, and scientific issues that were considered during the planning and delivery of the lookback exercise. RESULTS:Development and delivery of a national lookback required robust governance, engagement of all relevant stakeholders and a shared understanding of aims, effective communication, systems, resources, limitations, and project management. Outcomes included a high testing uptake, low levels of reported anxiety, and a comprehensive data set. CONCLUSION:Key aspects for delivery of a successful large-scale lookback program include a patient-centered approach, clear and accessible communication, and whole-systems multiagency collaboration. Major challenges include stakeholder engagement and capacity.

The cornerstone of life-saving therapy in immune-mediated thrombotic thrombocytopenic purpura (iTTP) has been plasma exchange (PEX) combined with immunomodulatory strategies. Caplacizumab, a novel anti-von Willebrand factor nanobody trialed in 2 multi-center randomized controlled trials (RCTs) leading to European Union and US Food and Drug Administration approval, has been available in the United Kingdom (UK) through a patient access scheme. Data were collected retrospectively from 2018 to 2020 for 85 patients (4 children) receiving caplacizumab from 22 UK hospitals. Patient characteristics and outcomes in the real-world clinical setting were compared with caplacizumab trial end points and historical outcomes in the precaplacizumab era. Eighty-four of 85 patients received steroid and rituximab alongside PEX; 26% required intubation. Median time to platelet count normalization (3 days), duration of PEX (7 days), and hospital stay (12 days) were comparable with RCT data. Median duration of PEX and time from PEX initiation to platelet count normalization were favorable compared with historical outcomes (P <.05). Thrombotic thrombocytopenic purpura (TTP) recurred in 5 of 85 patients; all had persistent ADAMTS13 activity < 5 IU/dL. Of 31 adverse events in 26 patients, 17 of 31 (55%) were bleeding episodes, and 5 of 31 ( 16%) were thrombotic events ( 2 unrelated to caplacizumab); mortality was 6% ( 5/ 85), with no deaths attributed to caplacizumab. In 4 of 5 deaths, caplacizumab was introduced >48 hours after PEX initiation (3-21 days). This real-world evidence represents the first and largest series of TTP patients, including pediatric patients, receiving caplacizumab outside of clinical trials. Representative of true clinical practice, the findings provide valuable information for clinicians treating TTP globally.

Congenital thrombotic thrombocytopenic purpura (cTTP) is an ultra-rare thrombomi-croangiopathy caused by an inherited deficiency of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). There are limited data on genotype-phenotype correlation; there is no consensus on treatment. We reviewed the largest cohort of cTTP cases, diagnosed in the United Kingdom, over the past 15 years. Seventy-three cases of cTTP were diagnosed, confirmed by genetic analysis. Ninety-three percent were alive at the time of review. Thirty-six percent had homozygous mutations; 64% had compound heterozygous mutations. Two presentation peaks were seen: childhood (median diagnosis age, 3.5 years) and adulthood, typically related to pregnancy (median diagnosis age, 31 years). Genetic mutations differed by age of onset with prespacer mutations more likely to be associated with childhood onset (P = .0011). Sixty-nine percent of adult presentations were associated with pregnancy. Fresh-frozen plasma (FFP) and intermediate purity factor VIII concentrate were used as treatment. Eighty-eight percent of patients with normal blood counts, but with headaches, lethargy, or abdominal pain, reported symptom resolution with prophylactic therapy. The most common currently used regimen of 3-weekly FFP proved insufficient for 70% of patients and weekly or fortnightly infusions were required. Stroke incidence was significantly reduced in patients receiving prophylactic therapy (2% vs 17%; P = .04). Long-term, there is a risk of end-organ damage, seen in 75% of patients with late diagnosis of cTTP. In conclusion, prespacer mutations are associated with earlier development of cTTP symptoms. Prophylactic ADAMTS13 replacement decreases the risk of end-organ damage such as ischemic stroke and resolved previously unrecognized symptoms in patients with nonovert disease.

A 51-year-old woman presented to the Emergency Department with a five day history of general malaise, fevers, and myalgia. Two days before, she developed dark red discoloration of her urine, containing what she described as “blood clots.” Subsequently, her urine became dark and “coca-cola” colored. Her general practitioner prescribed co-amoxiclav for possible urinary tract infection. Despite this, she developed increasing back and flank pain, and experienced rigors. On the day of admission, she started vomiting and had diarrhea, but had no evidence of melaena or hematemesis. Her past medical history included benign thyroid nodules and an appendicectomy. She took no regular medications. She smoked 5 cigarettes per day but only rarely drank alcohol. Her presentation with a febrile illness, flank pains, and urinary symptoms including frank “hematuria” suggests urinary tract pathology. Clots are not typical of pyelonephritis and suggest urinary tract hemorrhage. The subsequent “coca cola” urine is more typical of some forms of glomerulonephritis. It could also represent other urinary pigments such as myoglobin. The differential diagnoses at this stage include urinary tract infection with hemorrhage, glomerulonephritis, or rhabdomyolysis. The patient was jaundiced and pale. She was afebrile but hypotensive (blood pressure 93/57 mm Hg), with a normal pulse rate and respiratory observations. Cardiovascular and respiratory examinations were normal, and her abdomen was soft and not tender. There was no renal angle tenderness. Urine dipstick testing was positive for blood, nitrites, and leukocytes. She was treated with piperacillin-tazobactam for presumed sepsis. Urinary tract pathology is not typically associated with jaundice, yet the normal abdominal examination argues against cholangitis. Nevertheless, there is a suspicion of sepsis given her history of rigors and hypotension. Pallor with jaundice should also suggest hemolysis. Key results over time are shown in Table 1. Her full blood count was relatively normal, other than a mild neutrophilia. She had an acute kidney injury and hyperbilirubinaemia (Table 1) with otherwise normal liver function, and normal sodium, potassium, and creatinine kinase (CK). Elevated bilirubin with otherwise normal liver function suggests prehepatic jaundice ie, hemolysis. The hemoglobin level at presentation is almost normal, but 6 months previously her hemoglobin was 140 g/L, suggesting a reduction linked to her current illness. This prompted a search for hemolysis. The acute kidney injury is concerning. It may be due to sepsis though the blood pressure is only slightly low. The history was felt to be too short for an acute glomerulonephritis. The haptoglobin was low, and the direct antiglobulin test (DAT), was C3d positive (2+), IgG negative. Lactate dehydrogenase (LDH) was markedly elevated at 2057 Units/L. Reticulocytes were normal (Table 1). The blood film showed no fragments, spherocytes or polychromasia (Figure 1A). Repeat urinalysis showed no casts, red cells or organisms on direct microscopy, and no growth at 24 hours. Blood film from Day 1 (A) and 4 (B) of admission. The first film is normal, but the second shows thrombocytopenia and numerous red cell fragments (arrowheads)—indicating microangiopathy [Color figure can be viewed at wileyonlinelibrary.com] The clinical features fit intravascular hemolysis (rigors, flank pains, urine discolored by hemoglobin), and a high LDH with low haptoglobin is consistent with this. Reticulocytes are often normal in acute hemolysis. Absence of red cells with a positive urine dipstick test for blood is consistent with hemoglobinuria (or myoglobinuria, but note the normal CK). The complement-positive DAT suggests cold rather than warm immune hemolysis. The most common cold hemolysis is cold hemagglutinin disease (CHAD), but features such as flank pain—that suggest a brisk hemolysis happening in warmer vasculature—are not typical. This raised the prospect of paroxysmal cold-hemoglobinuria (PCH). A working diagnosis of cold hemolysis was made, and the patient was kept warm, with a plan made to manage with transfusions as required. She was prescribed folic acid to aid hematopoiesis. Serum was tested for Donath-Landsteiner antibodies. The result was positive: a biphasic hemolysin was detected, maximum titre 1/16 (papainised cells at 4°). The patient's phenotype was A RhdD negative, rr, K negative, P1 positive. The positive Donath-Landsteiner test confirms the diagnosis of PCH and fits the presentation here. Cold hemolysis, including PCH, is generally treated conservatively with warming measures to prevent antibody-red cell binding and hemolysis. Red cell transfusion is reserved for severe and life-threatening hemolysis, and is typically given through a blood-warmer. The acute kidney injury was attributed to free hemoglobin causing toxic acute tubular injury. Management is supportive, with fluid and renal replacement therapy if required. The cause of the urinary “clots” is unclear though papillary necrosis could give that appearance. On day 2 and 3, despite intravenous hydration and warming, her renal function and anemia worsened (Table 1). By day 4 her hemoglobin was 67 g/L, and her platelets fell to 61 × 109/L. A blood film showed evidence of microangiopathy with 8 red cell fragments per ×50 high-power-field, hpf (Figure 1B). The coagulation screen remained normal, but her renal function continued to deteriorate with creatinine rising from 576 µmol/L on day 3 to 781 µmol/L on day 4 (Table 1). Thrombocytopenia is not typical of PCH, and, in combination with acute kidney injury and red cell fragmentation, raises the prospect of thrombotic microangiopathies. The thrombocytopenia is not severe and there is no neurological impairment to suggest thrombotic thrombocytopenic purpura (TTP), though these may not be found at presentation. There is no history of bloody diarrhea to suggest hemolytic uremic syndrome (stool sample was negative for Escherischa coli O157). The patient is postmenopausal, excluding pregnancy-associated causes. There was no evidence of antiphospholipid syndrome—her coagulation screen was normal and antiphospholipid antibodies were not detected. Intravascular hemolysis can cause acute kidney injury and disseminated intravascular coagulation with microangiopathy and platelet consumption, though we would expect the coagulation screen to be abnormal. Given the positive Donath-Landsteiner test and lack of a convincing alternative diagnosis, the patient continued to be treated conservatively for PCH. On day 4, as her renal function continued to deteriorate rapidly (Table 1) and she was now oligo-anuric, she began hemodiafiltration through a central venous catheter using a warmed circuit. This was poorly tolerated: she had a hypotensive episode after 1 hour of treatment. The procedure was abandoned. On day 5 she became drowsy, felt more unwell and had a temperature of 38.1°C. There were no new focal examination findings. Her hemoglobin remained low and the platelets fell to 57 × 109/L. Hemodiafiltration was chosen over other forms of renal replacement therapy due to improved clearance of higher molecular weight toxins including hemoglobin (see discussion). The hypotensive episode may relate to acute hemolysis. Despite serological evidence of PCH and appropriate treatment, she had clinically deteriorated. The possibility of TTP remained, particularly given the drowsiness and fever. Therapy options were reviewed. Steroids can be used in both conditions. Plasma exchange is the cornerstone of TTP therapy, but has also been used successfully in PCH. The patient started prednisolone 1 mg/kg. Samples were sent to test ADAMTS13 levels, and plasma exchange begun. Despite aggressive warming procedures—nursing in an overheated room (24°C), use of a warm-air blanket and a heated circuit—plasma exchange proved impossible. Venous blood leaving the patient became visibly pale and transparent in the circuit. The machine automatically prevented fluid return. Exchange was stopped, and the patient was given further red cell transfusion and 1 g/kg intravenous immunoglobulin. The striking change in the appearance of the blood seems to represent intra-circuit hemolysis due to the PCH hemolysin. In PCH antibodies bind to cool blood (<20°C in vitro) and cause complement-dependent hemolysis on rewarming. The circuit mechanics mimicked this physiology resulting in dramatic hemolysis. This supports the diagnosis of PCH. Intravenous immunoglobulin may be used in life threatening situations, but is mainly expected to treat extravascular hemolysis. By Day 6 her condition improved. Her hemoglobin and platelet count rose and her blood film showed fewer fragments. She tolerated a full session of haemodiafiltration with both a warmed circuit and lines under a warm-air blanket. She received a second dose of intravenous immunoglobulin. Over the next 5 days she had further transfusions and renal replacement therapy, but made a steady clinical improvement. ADAMTS13 levels were normal. Tests for underlying cause of PCH were negative, including influenza A and B, respiratory syncytial virus, adenovirus and Mycoplasma pneumonia PCR and TrepenomaI IgG. CT chest, abdomen and pelvis showed no underlying malignancy. By Day 15 her renal function and hematological results were returning to normal and she was discharged home. Her steroids were tapered to stop over 3 months; laboratory parameters had normalized and she has made a full recovery. The final diagnosis is PCH triggered by an unidentified infective episode. The intravascular hemolysis caused microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury attributed to hemoglobin-mediated toxic acute tubular injury. This case demonstrates decision making around intravascular hemolysis, and describes unusual complications of severe paroxysmal cold hemoglobinuria in an adult. In particular, the degree of thrombocytopenia and acute kidney injury are rarely described. PCH is a rare cause of autoimmune hemolytic anemia in adults,1 but may be the most common cause in children.2 PCH is caused by an antibody hemolysin that binds the P1 antigen on erythrocytes at low temperature, then triggers complement activation on rewarming to 37°C.2 This is the basis of the Donath-Landsteiner test: patient serum does not hemolyse reagent red cells at 37°C unless the mixture has already been incubated at 0°C. PCH in children is usually attributed to antecedent viral illness.3 In adults this may be the case, but was historically related to secondary and tertiary syphilis.2, 4 Other causes include malignancy and autoimmune disease.1 Presentation is with features of severe intravascular hemolysis—fever, rigors, jaundice, hemoglobinuria, and pallor. Diagnosis is based on the identification of a complement-positive DAT and the Donath–Landsteiner test. The condition must be distinguished from CHAD which also presents with intravascular hemolysis but is often subacute or chronic, and not usually associated with the constitutional features seen in PCH.2 There are serological differences too. CHAD is classically mediated by a cold-reactive antibody against i or I antigens that does not show the biphasic activity seen in PCH, and the antibody titre is typically >1:500 in CHAD but <1:64 in PCH.5 Acute kidney injury is reported only rarely in PCH,6 but other causes of intravascular hemolysis can cause haem-induced acute tubular injury.7 In health, haptoglobin binds free hemoglobin, but in intravascular hemolysis the free hemoglobin saturates this system and can cross the glomerular filtration barrier. In the nephron, heme pigment causes intrarenal vasoconstriction, intratubular cast formation, and direct cytotoxic effects including membrane disruption and DNA damage.8 Nevertheless, heme-induced acute kidney injury rarely requires dialysis, usually resolving with conservative measures.9 In acute kidney injury caused by myoglobinuria, there is rationale for using hemodiafiltration over other forms of renal replacement therapy because it may help clear the higher molecular weight toxic molecules10; this should also be the case for hemoglobinuria. In PCH, platelet counts are said to be normal or high2; significant microangiopathy with thrombocytopenia is not described. Microangiopathy does, however, occur in disseminated intravascular coagulation,11 a known complication of intravascular hemolysis due to liberation of thromboplastin-like substances.12 While the coagulation screen was normal in this case we assume the mechanism is similar. The clinical course in infection-associated PCH is generally self-limiting.4 Historical cases related to syphilis were often recurrent.3 Treatment is supportive with warming, folate replacement and red cell transfusion; corticosteroids are reserved for life-threatening hemolysis.4, 13 Plasma exchange has been reported twice, with the rationale of removing circulating hemolysins and arresting hemolysis14, 15; neither report identifies the problem with intra-circuit hemolysis described above. Various alternative treatments are reported, including the anti-CD20 antibody rituximab,16 and cyclophosphamide.17 Eculizumab might be expected to halt hemolysis due to its terminal-complement inhibition,3 but the only report of its use was disappointing.17 In conclusion this case represents the potential difficulties in distinguishing PCH from other hemolytic and non-hemolytic causes of anemia with constitutional symptoms, urinary abnormalities and fever. It highlights some of the diagnostic challenges introduced by the unexpected severe thrombocytopenia and acute kidney injury. We believe the description of apparent intra-circuit hemolysis in plasma exchange for PCH is unique.