A case of disseminated intravascular coagulation following tumour lysis syndrome due to small cell carcinoma of the lung.

A 64-year-old man was diagnosed with small cell lung cancer (SCLC) with multiple bone and liver metastases and bone marrow metastases. Spontaneous tumour lysis syndrome (TLS) was observed before starting chemotherapy with carboplatin, etoposide, and atezolizumab. The tumour further collapsed, and the patient developed disseminated intravascular coagulation (DIC) on day 4 of chemotherapy. The patient was successfully treated with intravenous hydration and rasburicase for TLS and subcutaneous unfractionated heparin for DIC. A large amount of tissue factor may be released in TLS, which could induce DIC. However, to the best of our knowledge, this is the first report of DIC following TLS in a case of SCLC. DIC following TLS in SCLC is a rare but life-threatening oncologic complication. Therefore, clinicians should be aware of this possibility when treating patients with advanced SCLC.

Sepsis-Associated DIC with Decreased Levels of Antithrombin and Fibrinogen is the Target for Combination Therapy with Thrombomodulin Alfa and Antithrombin.

Background Disseminated intravascular coagulation (DIC) is not a homogeneous condition, but rather includes heterogeneous conditions, and its pathophysiology and outcome vary considerably depending on the background. Although anticoagulant therapy is expected to be of benefit in the treatment of DIC, previous studies have suggested that the benefits are limited only to a specific subtype. Objects The purpose of this study was to identify the group that would benefit from combination therapy using thrombomodulin/antithrombin. Methods The data from 2,839 patients registered in the postmarketing surveillance of thrombomodulin were evaluated. The patients were divided into four groups depending on antithrombin and fibrinogen levels, and the additive effects of antithrombin on thrombomodulin were examined in the groups. Results The DIC score, Sequential Organ Failure Assessment score, and mortality were significantly higher in the DIC group with low-antithrombin/low-fibrinogen than in the DIC groups without either low antithrombin or low fibrinogen. The survival curve was significantly higher in DIC patients with combination therapy than in patients treated with thrombomodulin monotherapy, but this effect was seen only in patients with infection-based DIC. Conclusion DIC patients with low-antithrombin/low-fibrinogen risk poor outcomes, but they can be the target of combination therapy with antithrombin and thrombomodulin as long as the DIC is due to infection.

Clinical Features of Disseminated Intravascular Coagulation According to the French-American-British Classification in Patients With Acute Leukemia and Thrombomodulin Alfa Treatment-A Cohort Study Using a Postmarketing Surveillance Database.

The aims of this study were to analyze the clinical features of a large number of cases with disseminated intravascular coagulation (DIC) associated with acute leukemia and to assess the safety and efficacy of thrombomodulin alfa (TM-α) using the French-American-British (FAB) classification of hematological malignancies. We retrospectively examined 644 patients with acute leukemia in postmarketing surveillance for TM-α. M3, M2, M4, M1, and M5 subtypes of acute myeloid leukemia (AML) and L2 and L1 subtypes of acute lymphoblastic leukemia (ALL) have been found more frequently among patients with DIC. Bleeding symptoms at baseline were more frequent in M3 and M7 subtypes. Fibrinogen concentrations were lower, and plasmin-plasmin inhibitor complex values were higher in M3 and Philadelphia-positive (Ph+) ALL. Overall DIC resolution rate was 60.2%, higher in L1 and Ph+ ALL, lower in M1, and generally higher in ALL than in AML. Overall survival rate was generally high, at 79.8%, with higher rates in L3, Ph+ ALL, and M3. Regardless of FAB subgroup, TM-α showed improved bleeding symptoms and DIC scores in clinical practice for DIC patients with acute leukemia.

A novel homozygous variant of the thrombomodulin gene causes a hereditary bleeding disorder.

We report a 19-year-old Vietnamese woman who experienced several life-threatening bleeding events, including ovarian hemorrhage. Blood analysis revealed a decreased fibrinogen level with markedly elevated fibrinogen/fibrin degradation products and D-dimer levels. Despite hemostatic surgery and administration of several medications, such as nafamostat mesylate, tranexamic acid, and unfractionated heparin, the coagulation abnormalities were not corrected, and the patient experienced repeated hemorrhagic events. We found that administration of recombinant human thrombomodulin (rhTM) remarkably improved the patient's pathophysiology. Screening and sequencing of the TM gene (THBD) revealed a previously unreported homozygous variation: c.793T>A (p.Cys265Ser). Notably, the Cys265 residue forms 1 of 3 disulfide bonds in the epidermal growth factor (EGF)-like domain 1 of TM. Transient expression experiments using COS-1 cells demonstrated markedly reduced expression of TM-Cys265Ser on the plasma membrane relative to wild-type TM. The TM-Cys265Ser mutant was intracellularly degraded, probably because of EGF-like domain 1 misfolding. The reduced expression of TM on the endothelial cell membrane may be responsible for the disseminated intravascular-coagulation-like symptoms observed in the patient. In summary, we identified a novel TM variant, c.793T>A (p.Cys265Ser). Patients homozygous for this variant may present with severe bleeding events; rhTM should be considered a possible treatment option for these patients.

An evaluation of the Japanese Society on Thrombosis and Hemostasis criteria for disseminated intravascular coagulation as a predictor of prognosis in patients with infection.

INTRODUCTION: A criterion for disseminated intravascular coagulation (DIC) that reflects the status of controlled coagulopathy would be useful for determining when to stop treatment. Use of the DIC criteria of the Japanese Society on Thrombosis and Hemostasis (JSTH) for predicting the outcome during recombinant soluble thrombomodulin (thrombomodulin alfa, TM-α) treatment was evaluated. METHODS: A retrospective, multicenter survey was conducted in 798 medical facilities in Japan. Of the 4342 patients who underwent TM-α treatment, 193 with infection-associated DIC were investigated. RESULTS: The 28-day mortality rate increased with the increase in JSTH DIC scores at the end of TM-α treatment, with a Cramer's coefficient of association of 0.431. A reduced platelet count (odds ratio [OR]: 0.847, P < .001), prolonged prothrombin time ratio (OR: 5.681, P < .001), decreased fibrinogen level (OR: 0.995, P < .001), higher level of fibrinogen and fibrin degradation products (OR: 1.009, P = .026), and lower antithrombin activity (OR: 0.973, P < .001) were correlated with 28-day mortality. On multivariate analysis, the JSTH DIC score at the completion of TM-α therapy was a predictor of mortality (OR: 1.591, 95% CI: 1.219-2.077). CONCLUSION: The JSTH DIC score at the end of anticoagulation therapy may be a reliable tool for predicting the outcome in patients with infection-associated DIC.

Hypofibrinogenemia is associated with a high degree of risk in infectious diseases: a post-hoc analysis of post-marketing surveillance of patients with disseminated intravascular coagulation treated with thrombomodulin alfa.

BACKGROUND: In patients with infectious diseases, disseminated intravascular coagulation (DIC) is often diagnosed without the fibrinogen value. The relationship between hypofibrinogenemia and outcomes of DIC in infectious diseases has thus remained unclear. METHODS: We analyzed 3204 patients who received with thrombomodulin alfa (TM-α) for DIC and suspected DIC. Hypofibrinogenemia was defined by a fibrinogen level < 1.5 g/L. RESULTS: Hypofibrinogenemia was observed in 10.3% of patients with infectious diseases. The frequencies of both bleeding and organ failure symptoms, and the scores for organ failure or the DIC diagnostic criteria were significantly higher in infectious disease patients with hypofibrinogenemia, suggesting that in patients with infectious diseases, hypofibrinogenemia is associated with more progressive and severe DIC. Although the 28-day survival rate and the DIC resolution rate were both significantly lower for infectious disease patients with DIC with hypofibrinogenemia than for those without hypofibrinogenemia, this difference was not observed in DIC patients with hematological diseases. CONCLUSIONS: Hypofibrinogenemia among infectious disease patients with DIC may reflect increased consumption of fibrinogen due to accelerated coagulation reactions, while hypofibrinogenemia among hematological disease patients with DIC may be caused by fibrinogenolysis due to hyperfibrinolysis, and frequently results in bleeding and multiple-organ failure.

Severe Antithrombin Deficiency May be Associated With a High Risk of Pathological Progression of DIC With Suppressed Fibrinolysis.

The frequency of severe antithrombin deficiency (SAD) was examined in the hematopoietic disorder-, infectious-, and basic-types of the disseminated intravascular coagulation (DIC). A posthoc analysis of 3008 DIC patients (infectious-type, 1794; hematological disorder-type, 813; and basic-type, 401) from post-marketing surveillance data of thrombomodulin alfa was performed. The clinical features of patients and outcomes were compared between patients with and without SAD, using an antithrombin cutoff value of 50%. Patients with SAD accounted for 40.4% of infectious-type DIC, 8.0% of hematopoietic disorder-type DIC, and 26.7% of basic-type DIC. There was no significant difference in thrombin-antithrombin complex levels between patients with and without SAD. The decreased fibrinogen level and differences in clinical features were significantly greater but the increases in fibrinolytic markers were significantly lower in patients with SAD than in those without. The 28-day survival rate was significantly lower in patients with SAD than in those without. Severe antithrombin deficiency was observed in all types of DIC, including hematopoietic disorders. Both hypofibrinolysis and hypercoagulability in patients with SAD may cause multiple organ failure and poor outcomes.

Analysis of the association between resolution of disseminated intravascular coagulation (DIC) and treatment outcomes in post-marketing surveillance of thrombomodulin alpha for DIC with infectious disease and with hematological malignancy by organ failure.

BACKGROUND: Although disseminated intravascular coagulation (DIC) is life-threatening, any organ failure associated with DIC resolution and outcomes have been unclear. PATIENTS AND METHODS: A total of 2795 DIC patients (infection: 1990, hematological malignancy: 805) were analyzed in the post-marketing surveillance of thrombomodulin alpha (TM-α). The background factors of sequential organ failure assessment (SOFA) and antithrombin (AT) were investigated in DIC with infectious disease for their association with DIC resolution and outcome using κ statistics, indicating DIC resolution and survival or DIC non-resolution and non-survival. The same analyses were performed for total bilirubin, creatinine, lactate dehydrogenase, and underlying disease in DIC with hematological malignancy. RESULTS: In DIC with infectious disease, higher SOFA score severity was closely correlated with lower overall survival in both the DIC resolution and non-resolution groups, but AT activity was not. κ coefficients were 0.234, 0.295, and 0.311 for the SOFA score 0-6, 7-12, and 13-24 groups, respectively. In DIC with hematological malignancy, κ coefficients of total bilirubin were 0.251 and 0.434, and those of creatinine were 0.283 and 0.437 in the normal and abnormal groups, respectively, showing better concordance in the abnormal group than in the normal. Other factors had poor concordance. CONCLUSION: In DIC with infectious disease, DIC resolution is an important therapeutic target in patients who have higher SOFA score severity. In DIC with hematological malignancy, DIC resolution is similarly important in patients with abnormality of bilirubin and/or creatinine. TRIAL REGISTRATION: The clinical characteristics and treatment outcomes of patients with DIC treated with TM-α between May 2008 and April 2010 were retrospectively analyzed by subgroup analysis of the post-marketing surveillance data.

The approval of revised diagnostic criteria for DIC from the Japanese Society on Thrombosis and Hemostasis.

As proposed diagnostic criteria for DIC from the Japanese Society on Thrombosis and Hemostasis has been approved and revised, the contents and changes are informed.

[Management of Venous Thromboembolism in Cancer Patients].

The clinical relevance of the association between venous thromboembolism(VTE)and cancer is well documented. VTE is one of the leading causes of death in cancer patients. It would be an advantage to have knowledge on predictive parameters for the development of thrombosis and to be able to select cancer patients individually according to their riskprofiles. An elevated platelet count is associated with an increased riskof VTE in cancer patients. The biomarkers including D-dimer have been identified and used to extend the existing riskstratification. Treatment of VTE in cancer patients is complicated due to a high rate of recurrence in addition to a higher riskof bleeding during anticoagulation therapy. Current guidelines recommend low-molecular-weight heparin(LMWH)monotherapy over vitamin K antagonist(VKA)for the treatment of cancer-associated VTE. However, recent clinical study could not show any superior efficacy of LMWH over VKA in preventing VTE recurrence or overall mortality. The direct oral anticoagulants(DOACs)may be an effective treatment for VTE in cancer patients, although the riskreduction for recurrent VTE with the DOACs compared to LMWH has not been well assessed. Physicians should frequently re-evaluate the risk-benefit ratio of ongoing anticoagulation therapy in individual patient, in views of the overall clinical conditions including their quality of life and life expectancy.

Proposal for new diagnostic criteria for DIC from the Japanese Society on Thrombosis and Hemostasis.

Disseminated intravascular coagulation (DIC) is a serious disease that, in the presence of underlying disease, causes persistent, generalized, marked coagulation activation. Early treatment based on an appropriate diagnosis is very important for improving patients' prognosis, to which end diagnostic criteria play a key role. Several criteria have been proposed, but each has its strengths and weaknesses, and improved criteria are needed. Widespread use of coagulofibrinolytic markers has elucidated that the pathology of DIC differs greatly as a function of the underlying disease. Thus, discriminating use of DIC diagnostic criteria that take underlying diseases into account is important. DIC diagnostic criteria that are well known in Japan include the Japanese Ministry of Health and Welfare's old DIC diagnostic criteria (JMHW criteria), the International Society on Thrombosis and Haemostasis's DIC diagnostic criteria (ISTH criteria), and the Japanese Association for Acute Medicine's acute-stage DIC diagnostic criteria (JAAM criteria). Those criteria have their respective drawbacks: the sensitivity of the ISTH criteria is poor, the JAAM criteria cannot be applied to all underlying diseases, and the JMHW criteria have poor sensitivity in the case of infections, do not use molecular markers, and result in misdiagnosis. The Japanese Society on Thrombosis and Hemostasis's newly proposed provisional draft DIC diagnostic criteria (new criteria) use diagnostic criteria classifications of "hematopoietic disorder type", "infectious type", and "basic type" based on the underlying pathology. For the hematopoietic disorder type the platelet count is omitted from the score, while for the infectious type, fibrinogen is omitted from the score. Also, points are added if the platelet count decreases with time. In the new criteria, molecular markers and antithrombin activity have been newly included, and as a countermeasure for misdiagnosis, 3 points are deducted if there is liver failure. In this paper, we discuss various problems encountered with DIC diagnosis, and we describe the new criteria together with the events that led to their creation. These new diagnostic criteria take into account the underlying diseases of wide area, and we expect that they will serve clinicians well due to the above adaptations and improvements.

The valuable diagnosis of DIC and pre-DIC and prediction of a poor outcome by the evaluation of diagnostic criteria for DIC in patients with hematopoietic injury established by the Japanese Society of Thrombosis and Hemostasis.

OBJECTIVE: We evaluated the modified diagnostic criteria for disseminated intravascular coagulation (DIC), which was published by the Japanese Society of Thrombosis and Hemostasis (JSTH), in 274 suspected DIC patients with hematopoietic injury. MATERIALS AND METHODS: The diagnoses of the patients were as follows: DIC (n=125); pre-DIC (n=42) and non-DIC (n=107). The efficacy of the diagnostic criteria for DIC was evaluated using a receiver operating characteristic (ROC) analysis. RESULTS: The area under the curve (ARC) and odd's ratio for the global coagulation test (GCT) scores in the diagnosis of "DIC" were high, while those for the diagnosis of "DIC and pre-DIC" were low, suggesting that the addition of antithrombin (AT) and soluble fibrin (SF)/thrombin antithrobin complex (TAT) was required to diagnose "DIC and pre-DIC". Although the addition of the AT and SF/TAT values to the GCT did not increase its ability to predict a poor outcome, the JSTH's modified diagnostic criteria scores were correlated with the odds ratio for death. DISCUSSION AND CONCLUSION: The JSTH's modified diagnostic criteria for DIC, which included the GCT score, and the AT, and TAT/SF values, were useful for diagnosing DIC and pre-DIC, and predicting a poor outcome.

Recent advances in disseminated intravascular coagulation: endothelial cells and fibrinolysis in sepsis-induced DIC.

Endothelial cells are highly active, sensing and responding to signals from extracellular environments. They act as gatekeepers, mediating the recruitment and extravasation of proinflammatory leukocytes to the sites of tissue damage or infection. Endothelial cells participate in fibrinolysis by secreting tissue-type plasminogen activator, which converts plasminogen to active enzyme plasmin through constitutive and regulated pathways. Fibrinolysis systems and inflammation are tightly linked, as both responses are major host defense systems against both healing processes of tissue repair as well as pathogenic microorganisms. Endothelial cell dysfunction is one of the early signs of systemic inflammation, and it is a trigger of multiple organ failure in sepsis. The marked increase in plasminogen activator inhibitor-1 level causes fibrinolytic shutdown in endotoxemia or sepsis and is one of the most important predictors of multiple organ dysfunction during sepsis-induced disseminated intravascular coagulation (DIC). Leukocytes exhibit the first-line response to microorganisms. Leukocyte-derived elastase degrades cross-linked fibrin to yield molecular species distinct from those generated by plasmin. The alternative systems for fibrinolysis that interact with the plasminogen activator-plasmin systems may play crucial roles in the lysis of fibrin clots in sepsis-induced DIC.

Living donor liver transplantation from an asymptomatic donor with mild coagulation factor IX deficiency: report of a case.

The use of donors with coagulation FIX deficiency is controversial, and there are no current protocols for peri-transplant management. We herein describe the first reported case of a pediatric LDLT from an asymptomatic donor with mild coagulation FIX deficiency. A 32-yr-old female was evaluated as a donor for her 12-month-old daughter with biliary atresia. The donor's pretransplant coagulation tests revealed asymptomatic mild coagulation FIX deficiency (FIX activity 60.8%). Freeze-dried human blood coagulation FIX concentrate was administered before the dissection of the liver and 12 h afterwards by bolus infusion (40 U/kg) and was continued on POD 1. The bleeding volume at LDLT was 590 mL. On POD 1, 3, 5, and 13, the coagulation FIX activity of the donor was 121.3%, 130.6%, 114.6%, and 50.2%, respectively. The donor's post-transplant course was uneventful, and the recipient is currently doing well at 18 months after LDLT. The FIX activity of the donor and recipient at nine months after LDLT was 39.2% and 58.0%, respectively. LDLT from donors with mild coagulation FIX deficiency could be performed effectively and safely using peri-transplant short-term coagulation FIX replacement and long-term monitoring of the plasma FIX level in the donor.

[Plasminogen activation and regulation of fibrinolysis].

Plasminogen activator-plasmin system is the central role for thrombus degradation. The system is finely tuned to allow healing of a blood vessel lesion without compromising the stability of the fibrin thrombus, and to localize fibrinolytic activity to the damaged area. There is a dynamic balance between fibrinolytic factors (plasminogen activators and plasmin) and inhibitory proteins (PAL-1, alpha2-plasmin inhibitor, and TAFIa). An alternative pathway for fibrinolysis that comprises leukocyte elastase and its interaction with the plasminogen activator-plasmin system has been suggested.

Combination of thrombin-antithrombin complex, plasminogen activator inhibitor-1, and protein C activity for early identification of severe coagulopathy in initial phase of sepsis: a prospective observational study.

INTRODUCTION: Current criteria for early diagnosis of coagulopathy in sepsis are limited. We postulated that coagulopathy is already complicated with sepsis in the initial phase, and severe coagulopathy or disseminated intravascular coagulation (DIC) becomes overt after progressive consumption of platelet and coagulation factors. To determine early diagnostic markers for severe coagulopathy, we evaluated plasma biomarkers for association with subsequent development of overt DIC in patients with sepsis. METHODS: A single-center, prospective observational study was conducted in an adult ICU at a university hospital. Plasma samples were obtained from patients with sepsis at ICU admission. Fourteen biomarkers including global markers (platelet count, prothrombin time, activated partial thromboplastin time, fibrinogen and fibrin degradation product (FDP)); markers of thrombin generation (thrombin-antithrombin complex (TAT) and soluble fibrin); markers of anticoagulants (protein C (PC) and antithrombin); markers of fibrinolysis (plasminogen, α2-plasmin inhibitor (PI), plasmin-α2-PI complex, and plasminogen activator inhibitor (PAI)-1); and a marker of endothelial activation (soluble E-selectin) were assayed. Patients who had overt DIC at baseline were excluded, and the remaining patients were followed for development of overt DIC in 5 days, and for mortality in 28 days. RESULTS: A total of 77 patients were enrolled, and 37 developed overt DIC within the following 5 days. Most patients demonstrated hemostatic abnormalities at baseline with 98.7% TAT, 97.4% FDP and 88.3% PC. Most hemostatic biomarkers at baseline were significantly associated with subsequent development of overt DIC. Notably, TAT, PAI-1 and PC discriminated well between patients with and without developing overt DIC (area under the receiver operating characteristic curve (AUROC), 0.77 (95% confidence interval, 0.64 to 0.86); 0.87 (0.78 to 0.92); 0.85 (0.76 to 0.91), respectively), and using the three together, significantly improved the AUROC up to 0.95 (vs. TAT, PAI-1, and PC). Among the significant diagnostic markers for overt DIC, TAT and PAI-1 were also good predictors of 28-day mortality (AUROC, 0.77 and 0.81, respectively). CONCLUSIONS: Severe coagulation and fibrinolytic abnormalities on ICU admission were associated with subsequent development of overt DIC. A single measurement of TAT, PAI-1, and PC activity could identify patients with ongoing severe coagulopathy, early in the course of sepsis.

Paxillin is an intrinsic negative regulator of platelet activation in mice.

BACKGROUND: Paxillin is a LIM domain protein localized at integrin-mediated focal adhesions. Although paxillin is thought to modulate the functions of integrins, little is known about the contribution of paxillin to signaling pathways in platelets. Here, we studied the role of paxillin in platelet activation in vitro and in vivo. METHODS AND RESULTS: We generated paxillin knockdown (Pxn-KD) platelets in mice by transplanting bone marrow cells transduced with a lentiviral vector carrying a short hairpin RNA sequence, and confirmed that paxillin expression was significantly reduced in platelets derived from the transduced cells. Pxn-KD platelets showed a slight increased in size and augmented integrin αIIbß3 activation following stimulation of multiple receptors including glycoprotein VI and G protein-coupled receptors. Thromboxane A2 biosynthesis and the release of α-granules and dense granules in response to agonist stimulation were also enhanced in Pxn-KD platelets. However, Pxn-KD did not increase tyrosine phosphorylation or intracellular calcium mobilization. Intravital imaging confirmed that Pxn-KD enhanced thrombus formation in vivo. CONCLUSIONS: Our findings suggest that paxillin negatively regulates several common platelet signaling pathways, resulting in the activation of integrin αIIbß3 and release reactions.

Changes in blood coagulation-fibrinolysis markers by pneumatic tourniquet during total knee joint arthroplasty with venous thromboembolism.

This study investigated changes in blood coagulation-fibrinolysis markers during total knee arthroplasty (TKA). Preoperative 16-row multidetector row computed tomography (MDCT) revealed no asymptomatic venous thromboembolism (VTE) in the 42 patients recruited. Using MDCT postoperatively, patients were divided into thrombus (asymptomatic VTE, 19 patients) and no-thrombus (23 patients) groups. Blood taken at intervals before and after pneumatic tourniquet release revealed increased plasminogen activator inhibitor type-1 (PAI-1) at 30s for both groups and at 90s (both P=0.01) in the thrombus group. D-dimer levels were highest at 30 and 90s for both groups (P = 0.01). PAI-1 and D-dimer levels were strongly correlated at both time points in the thrombus group. Inactivating fibrinolysis due to PAI-1 may lead to asymptomatic VTE after TKA.

The prevalence of neutralizing antibodies against adeno-associated virus capsids is reduced in young Japanese individuals.

Pre-existing antibodies against adeno-associated virus (AAV), caused by natural AAV infections, interfere with recombinant AAV vector-mediated gene transfer. We studied the prevalence of neutralizing antibodies against AAV serotypes 1, 2, 5, 8, and 9 in healthy subjects (n = 85) and hemophilia patients (n = 59) in a Japanese population. For healthy subjects, the prevalence of neutralizing antibodies against AAV serotypes 1, 2, 5, 8, and 9 was 36.5%, 35.3%, 37.6%, 32.9%, and 36.5%, respectively, while that in hemophilia patients was 39.7%, 28.8%, 35.6%, 32.9%, and 27.4%, respectively. There was no difference in the prevalence of neutralizing antibody against each AAV serotype between the healthy subjects and the hemophilia patients. The prevalence of neutralizing antibodies against all AAV serotypes increased with age in both healthy subjects and hemophilia patients. High titers of neutralizing antibodies against AAV2 (≥1:224) and AAV8 (≥1:224) were more evident in older individuals (≥42 years old). Approximately 50% of all screened individuals were seronegative for neutralizing antibodies against each AAV tested, while approximately 25% of individuals were seropositive for each AAV serotype tested. The prevalence of seronegativity for all AAV serotypes was 67.0% (healthy subjects, 68.6%; hemophilia patients, 65.0%) and 18.6% (healthy subjects, 20.5%; hemophilia patients, 15.7%) in young (<42 years old) and older subjects (≥42 years old), respectively. The findings from this study suggested that young subjects are more likely to be eligible for gene therapy based on AAV vectors delivered via an intravascular route because of the low prevalence of antibodies to AAV capsids.