Presence of lupus-type anticoagulant, in systemic lupus erythematosus and other clinical entities

The frequency of "Lupus anticoagulant" (LA), was studied in 51 patients with systemic lupus erythematosus (SLE), 15 patients with chronic immune thrombocytopenic purpura (ITP) and 3 other patients with prolonged partial thromboplastin time (PTT), two of which had suffered episodes of CVA, and the other had a diagnosis of Paroxysmal Nocturnal Hemoglobinuria. Lupus anticoagulant was determined in each patient by the plasma recalcification time and the Russell's viper venom clotting time. Eight patients with SLE, (15.6%) 6 with chronic ITP (40%) and the three patients with prolonged PTT were positive for LA. All patients with LA were female, whose ages ranged from 19 to 59 years, and all except two patients were under steroid therapy. Thrombocytopenia was the most frequent manifestation in the patients with LA, followed by recurrent fetal death and thrombosis. Only the patients with ITP had hemorrhagic complications and one of them also had CVA in one occasion. The immunosupressory therapy may have played a role in diminishing the frequency of LA in the patients studied.     

Warfarin sodium versus low-dose heparin in the long-term treatment of venous thrombosis.

Acute deep-vein thrombosis is usually treated with intravenous heparin for a number of days, then with oral anticoagulants for weeks to months. We have compared adjusted-dose warfarin sodium with fixed low-dose subcutaneous heparin in the prevention of recurrent deep-vein thrombosis. Sixty-eight patients with acute deep-vein thrombosis confirmed by venography were treated with intravenous heparin and then randomized to secondary prophylaxis. Nine of 35 patients receiving subcutaneous heparin, but none of 33 receiving warfarin sodium, had new episodes of objectively documented venous thromboembolism (P = 0.001). Seven patients on warfarin sodium experienced bleeding complications (of which four were major), as compared with no patients receiving subcutaneous heparin (P less than 0.005). Thus, adjusted-dose warfarin sodium is more effective than low-dose subcutaneous heparin in preventing recurrent venous thromboembolism, but its use is accompanied by a significant risk of bleeding.     

Acquired activated protein C resistance caused by lupus anticoagulants

Lupus anticoagulants (LA) can cause acquired activated protein C resistance (APC-R), but the clinical significance is unclear. To investigate thrombosis and acquired APC-R in patients with LA, we enrolled all 132 patients undergoing hypercoagulability testing with positive LA results and in whom APC-R (with factor V-deficient plasma) was performed during a 2.5-year period. Among 121 patients without factor V Leiden, 24.0% had acquired APC-R; retrospective and prospective (mean follow-up, 2.0 years) thrombotic events were analyzed. The distribution of venous vs arterial thrombosis was different for APC-R vs no APC-R (P = .0064). The majority (19/29 [66%]) with acquired APC-R experienced venous thrombosis, whereas a minority experienced arterial thrombosis (9/29 [31%]; P = .017). The opposite pattern occurred among patients without APC-R (arterial thrombi more common than venous thrombi). After excluding thrombotic events more than 5 years from a positive LA test, venous thrombosis occurred in 62% with (18/29) vs 32% without (29/92) APC-R (P = .0045); and arterial thrombosis in 28% with (8/29) vs 51% without (47/92) APC-R (P = .033). Patients with acquired APC-R due to LA had more venous thrombosis than did patients with LA without APC-R and experienced venous more often than arterial thrombosis.     

Deep-vein thrombosis and the incidence of subsequent symptomatic cancer.

BACKGROUND. In contrast to the established relation between overt cancer and subsequent venous thromboembolism, it is unclear whether symptomatic deep-vein thrombosis is associated with a risk of subsequent overt malignant disease. METHODS. Two hundred sixty consecutive patients with symptomatic, venographically proved deep-vein thrombosis were enrolled in a study, of whom 250 were followed during a two-year period. Among those assessed during follow-up, the incidence of subsequently detected cancer in the 105 patients with secondary venous thrombosis (i.e., thrombosis associated with a well-recognized risk factor other than cancer) was compared with the incidence of cancer in the 145 patients with idiopathic venous thrombosis. RESULTS. Routine examination at the time of diagnosis of the venous thrombosis revealed cancer in 5 of the 153 enrolled patients with idiopathic venous thrombosis (3.3 percent) and in none of the 107 enrolled patients with secondary venous thrombosis. During follow-up, overt cancer developed in 2 of the 105 patients with secondary venous thrombosis (1.9 percent) and in 11 of the 145 patients with idiopathic venous thrombosis (7.6 percent; odds ratio, 2.3; 95 percent confidence interval, 1.0 to 5.2; P = 0.043). Of the 145 patients with idiopathic venous thrombosis, 35 had confirmed recurrent thromboembolism. Overt cancer subsequently developed in 6 of the 35 (17.1 percent). The incidence of cancer in the patients with recurrent idiopathic venous thrombosis was higher than that in the patients with secondary venous thrombosis (P = 0.008; odds ratio, 9.8; 95 percent confidence interval, 1.8 to 52.2) or in the patients with idiopathic venous thrombosis that did not recur (P = 0.024; odds ratio, 4.3; 95 percent confidence interval, 1.2 to 15.3). CONCLUSIONS. There is a statistically significant and clinically important association between idiopathic venous thrombosis and the subsequent development of clinically overt cancer, especially among patients in whom venous thromboembolism recurs during follow-up.     

Antiphospholipid antibodies--our experience

Antiphospholipid antibodies (APA) have aroused multispeciality interests. In our study of 200 cases worked up for APA, we have used a few simple coagulation tests to detect lupus anticoagulant (LA) and ELISA to detect anticardiolipin antibodies. The positivity rate for LA among cases with recurrent pregnancy loss was 4.16% and for aCL 20.8%. The positivity rate for LA in patients with venous thrombosis was 6.2%, in arterial thrombosis was 7.14% and in SLE patients was 58.3%. In conclusion APAs are to be looked for in cases of recurrent pregnancy loss, thrombosis in people < 45 years of age without risk factors and SLE patients to assess the thrombotic risk and to decide on anti coagulant therapy for further management.     

Methods for detecting lupus anticoagulants and their relation to thrombosis and miscarriage in patients with systemic lupus erythematosus.

AIMS: To examine the sensitivity and specificity to past thrombotic events of four different coagulation tests, which screen for lupus anticoagulant (LA), and of anticardiolipin antibodies in patients with systemic lupus erythematosus. METHODS: Fifty three consecutive patients with systemic lupus erythematosus were studied of whom three males and 21 females, aged 21-60 years, had a history of venous and arterial thrombosis, or miscarriage, or both. Activated partial thromboplastin time (aPTT), dilute Russell's viper venom time (dRVVT), kaolin clotting time (KCT), dilute aPTT and the circulating titre of anticardiolipin antibodies were investigated in the two groups of patients and in 20 healthy control subjects. RESULTS: The prolonged dilute aPTT was more sensitive to thromboses or miscarriages, or both than dRVVT (p less than 0.05), KCT (p less than 0.01), and aPTT (p less than 0.001). No significant differences in specificity were found among aPTT (100%), dRVVT (93%), KCT (93%) and dilute aPTT (86.2%); but aPTT and dRVVT were significantly more specific (p less than 0.01, p less than 0.05, respectively) than anticardiolipin antibodies. CONCLUSIONS: The study shows a strong association between lupus anticoagulant and thrombosis when a very sensitive test such as the dilute aPTT is used. The combination of this assay with a very specific test such as dRVVT might enable patients with SLE at high risk of thrombosis to be identified.     

Fondaparinux compared with enoxaparin for the prevention of venous thromboembolism after elective major knee surgery.

BACKGROUND: Despite thromboprophylaxis, major knee surgery carries a high risk of venous thromboembolism. Fondaparinux, the first of a new class of synthetic antithrombotic agents, may reduce this risk. METHODS: In a double-blind study, we randomly assigned 1049 consecutive patients undergoing elective major knee surgery to receive subcutaneous doses of either 2.5 mg of fondaparinux once daily or 30 mg of enoxaparin twice daily, with both treatments initiated postoperatively. The primary efficacy outcome was venous thromboembolism up to postoperative day 11, defined as deep-vein thrombosis detected by mandatory bilateral venography, documented symptomatic deep-vein thrombosis, or documented symptomatic pulmonary embolism. The primary safety outcome was major bleeding. RESULTS: The primary efficacy outcome was assessed in 724 patients. The fondaparinux group had a significantly lower incidence of venous thromboembolism by day 11 (12.5 percent [45 of 361 patients]) than the enoxaparin group (27.8 percent [101 of 363 patients]; reduction in risk, 55.2 percent; 95 percent confidence interval, 36.2 to 70.2; P<0.001). Major bleeding (including overt bleeding with a bleeding index of 2 or more) occurred more frequently in the fondaparinux group (P=0.006), but there were no significant differences between the two groups in the incidence of bleeding leading to death or reoperation or occurring in a critical organ. CONCLUSIONS: In patients undergoing elective major knee surgery, postoperative treatment with 2.5 mg of fondaparinux once daily was significantly more effective in preventing deep-vein thrombosis than 30 mg of enoxaparin twice daily.     

Subcutaneous low-molecular-weight heparin compared with continuous intravenous heparin in the treatment of proximal-vein thrombosis.

BACKGROUND. Low-molecular-weight heparin has a high bioavailability and a prolonged half-life in comparison with conventional unfractionated heparin. Limited data are available for low-molecular-weight heparin as compared with unfractionated heparin for the treatment of deep-vein thrombosis. METHODS. In a multicenter, double-blind clinical trial, we compared fixed-dose subcutaneous low-molecular-weight heparin given once daily with adjusted-dose intravenous heparin given by continuous infusion for the initial treatment of patients with proximal-vein thrombosis, using objective documentation of clinical outcomes. RESULTS. Six of 213 patients who received low-molecular-weight heparin (2.8 percent) and 15 of 219 patients who received intravenous heparin (6.9 percent) had new episodes of venous thromboembolism (P = 0.07; 95 percent confidence interval for the difference, 0.02 percent to 8.1 percent). Major bleeding associated with initial therapy occurred in 1 patient receiving low-molecular-weight heparin (0.5 percent) and in 11 patients receiving intravenous heparin (5.0 percent), a reduction in risk of 91 percent (P = 0.006). This apparent protection against major bleeding was lost during long-term therapy. Minor hemorrhagic complications were infrequent. Ten patients receiving low-molecular-weight heparin (4.7 percent) died, as compared with 21 patients receiving intravenous heparin (9.6 percent), a risk reduction of 51 percent (P = 0.049). CONCLUSIONS. Low-molecular-weight heparin is at least as effective and as safe as classic intravenous heparin therapy under the conditions of this study and more convenient to administer. The simplified therapy provided by low-molecular-weight heparin may allow patients with uncomplicated proximal deep-vein thrombosis to be cared for in an outpatient setting.     

Clinical significance of anticardiolipin and anti-beta2-glycoprotein I antibodies

BACKGROUND: Anticardiolipin (aCl) and anti-beta2-glycoprotein I (anti-beta2-gpI) antibodies are autoantibodies associated with the antiphospholipid syndrome (APS), which is characterized by both arterial and venous thrombosis and miscarriages. The scope of this study was to explore the clinical characteristics of patients with aCl and anti-beta2-gpI antibodies. METHODS: ACl were tested in 3,600 consecutive sera in our laboratory between January 1999 and June 2001. The clinical diagnosis and prevalence of thrombosis and pregnancy morbidity were retrospectively reviewed in aCl-positive patients. Furthermore, the frequency of anti-beta2-gpI antibodies, lupus anticoagulant (LA), prolonged activated partial thromboplastin time (aPTT), and thrombocytopenia were investigated in aCl-positive patients. RESULTS: 147 aCl-positive patients, 110 women and 37 men with a mean age of 41 years (range 7.8-82.5), were identified. 42 (28.6%) aCl-positive patients fulfilled the criteria for APS which was secondary to a connective tissue disorder in 8 patients. The frequency of anti-beta2-gpI antibodies and LA, prolonged aPTT, and thrombocytopenia in aCl-positive patients was 23.8, 27.2, 25.7 and 9.2%, respectively. The presence of both aCl and anti-beta2-gpI antibodies was strongly associated with clinical symptoms of APS (p = 0.007) compared to p = 0.008 for LA. CONCLUSION: Our data suggest that assessment of anti-beta2-gpI antibodies in addition to aCl is a valuable diagnostic tool in the workup of patients with APS.     

Resting-state fMRI changes in Alzheimer's disease and mild cognitive impairment

Regional functional connectivity (FC) of 39 patients with Alzheimer's disease (AD), 23 patients with mild cognitive impairment (MCI), and 43 healthy elderly controls was studied using resting-state functional magnetic resonance imaging (rs-fMRI). After a mean follow-up of 2.8 ± 1.9 years, 7 MCI patients converted to AD, while 14 patients remained cognitively stable. Resting-state functional magnetic resonance imaging scans were analyzed using independent component analysis (ICA), followed by a "dual-regression" technique to create and compare subject-specific maps of each independent spatiotemporal component, correcting for age, sex, and gray matter atrophy. AD patients displayed lower FC within the default-mode network (DMN) in the precuneus and posterior cingulate cortex compared with controls, independent of cortical atrophy. Regional FC values of MCI patients were numerically in between AD patients and controls, but only the difference between AD and stable MCI patients was statistically significant. Correlation with cognitive dysfunction demonstrated the clinical relevance of FC changes within the DMN. In conclusion, clinically relevant decreased FC within the DMN was observed in AD.     

Detection of deep-vein thrombosis by real-time B-mode ultrasonography

In 220 consecutive outpatients with clinically suspected deep-vein thrombosis of the leg, we compared contrast venography with real-time B-mode ultrasonography, using the single criterion of vein compressibility with the ultrasound transducer probe. The common femoral and popliteal veins were evaluated for full compressibility (no thrombosis) and noncompressibility (thrombosis). Both veins were fully compressible in 142 of the 143 patients with normal venograms (specificity, 99 percent; 95 percent confidence interval, 97 to 100). All 66 patients with proximal-vein thrombosis had noncompressible femoral veins, popliteal veins, or both (sensitivity, 100 percent; 95 percent confidence interval, 95 to 100). For all patients (including 11 with calf-vein thrombi), sensitivity and specificity were 91 (95 percent confidence interval, 82 to 96) and 99 percent, respectively. The sensitivity for isolated calf-vein thrombosis was only 36 percent. The compression ultrasound test was repeated in a subset of 45 consecutive patients by a second examiner, unaware of the results of the first test, whose results agreed in all patients with those of the first examiner (kappa = 1). We conclude that ultrasonography with the single criterion of vein compressibility is a highly accurate, simple, objective, and reproducible noninvasive method for detecting proximal-vein thrombosis in outpatients with clinically suspected deep-venous thrombosis.     

The antiphospholipid antibody syndrome: A riddle wrapped in a mystery inside an enigma

The antiphospholipid antibody syndrome (APS) is the association of certain clinical features with the presence of antiphospholipid antibodies (APA) in the serum or plasma of affected individuals. APS may be primary or secondary to another disease, typically autoimmune diseases such as systemic lupus erythematosus (SLE).The prototypic clinical features are thrombotic events (venous and arterial) and pregnancy morbidity (recurrent fetal loss, severe preeclampsia, eclampsia, and multiple spontaneous abortions). The term antiphospholipid antibody is a misnomer since it now appears that APA are actually directed against protein phospholipid complexes. APA may also occur secondary to infections however these APA seem to be directed at phopsholipid only and are transient. Particular phospholipid-binding proteins associated with APS include beta 2-glycoprotein I (B2GPI), prothrombin, and annexin V. A recent International Consensus Statement defines Definite APS as the presence of certain clinical findings (either a thrombotic event and/or pregnancy morbidity) and the presence and persistence of laboratory evidence of APA [either the lupus anticoagulant (LA) and/or anticardiolipin antibodies (ACL)]. Other clinical features associated with APS include thrombocytopenia, various skin conditions, cardiac valvular diseases, and diverse neurological conditions as outlined in the main text. These other features may be part of APS but require further evidence to establish their pathological and clinical validity. Other laboratory tests of interest include anti-B2GPI, antiprothrombin, and antiphosphatidylserine antibodies. The diagnostic and clinical importance of these additional laboratory tests remains to be determined.APA are estimated to be present in up to 5% of the general population, with the prevalence increasing with age. APA are estimated to be present in 12% or more of patients with thrombosis. ACL are present in 12 to 30% of patients with SLE and LA are present in 15 to 34% of patients with SLE. There is often concordance between LA and ACL however this is not always true. APA (both ACL and LA) are associated with thromboembolic events. Venous thrombosis is more common than arterial thrombosis and a minority of patients have both. LA is more strongly associated with thrombosis than ACL. The estimated yearly incidence of thrombosis in individuals with APA is 1% for those with no history of thrombosis, 4% for those with SLE, and 6% for those with high titer immunoglobulin G (IgG) ACL. The presence of LA, and possibly of medium to high titers of IgG ACL, help identify patients at risk for thrombosis.     

Elevated plasminogen activator inhibitor levels found in patients with malignant conditions

Impaired fibrinolysis often is found in patients with deep-vein thrombosis. Deep-vein thrombosis is seen in some patients with malignant conditions. In patients with malignant conditions, impaired fibrinolysis may be present and may contribute to the development of thrombotic complications. In this study, the extrinsic fibrinolytic system was evaluated in a group of patients with malignant conditions and compared to a positive control group of patients with history of thrombosis but with no malignant condition and also to a negative control group of normal subjects. The group of patients with malignant conditions had plasminogen activator inhibitor levels similar to those patients with a history of thrombosis. Both of these groups had higher plasminogen activator inhibitor levels than the normal control patients.     

光化学诱导的血栓形成性脑缺血及其代谢改变

本文用光化学法激发大鼠局部脑血栓形成，以组织病理学、局部脑血流量、皮层水含量、三磷酸腺苷、二磷酸腺苷，一磷酸腺苷、能量负荷、肌酸及乳酸为指标，探讨局部脑血栓形成后５天ｒＣＢＦ明显增高的可能机理。结果表明，血栓形成后局部脑组织ＡＴＰ水平进行性减少（Ｐ＜０．０１）、ＡＤＰ／ＡＴＰ及ＡＭＰ／ＡＴＰ比值明显升高（Ｐ均＜０．０１），ＬＡ及脑水含量显著增加（Ｐ＜０．０１）。这些因素既是能量衰竭、无氧酵解的结果     

The effect of pituitary desensitization on ovarian volume measurements prior to in-vitro fertilization.

The measurement of ovarian volume has been recently shown to predict follicular response in in-vitro fertilization (IVF), specifically a lower number of retrieved oocytes with decreasing ovarian volume. This test appears to be better than basal follicle-stimulating hormone (FSH) as a prognostic measure of ovarian reserve. However, the effect of pituitary desensitization on ovarian volume has not been previously investigated. We prospectively evaluated 38 women undergoing IVF using a long luteal leuprolide acetate (LA) protocol. All women had their ovarian volume measurements performed on day 21, the day of LA start, and again on the day of gonadotrophin start. The mean age was 30.6 +/- 3.9 years (range 23-37). Basal FSH was 5.4 +/- 1.9 IU/l (range 1.2-10.2). The mean preLA ovarian volume was 7.0 +/- 3.6 cm3 (left ovary 6.8 +/- 3.9, right ovary 7.1 +/- 3.8), compared to 6.3 +/- 4.2 cm3 postLA (left ovary 6.0 +/- 4.9, right ovary 6.5 +/- 4.8) (not significant). The mean number of small antral follicles noted in both ovaries was also unchanged after pituitary desensitization. Pituitary desensitization using LA had no effect on overall ovarian volume measurements. The total number of retrieved oocytes decreased with increasing age and decreasing ovarian volume.     

Cerebral sinovenous thrombosis in children

BACKGROUND: Cerebral sinovenous thrombosis in children is a serious disorder, and information is needed about its prevention and treatment. METHODS: The Canadian Pediatric Ischemic Stroke Registry was initiated in 1992 at the 16 pediatric tertiary care centers in Canada. Children (newborn to 18 years of age) with symptoms and radiographic confirmation of sinovenous thrombosis were included. RESULTS: During the first six years of the registry, 160 consecutive children with sinovenous thrombosis were enrolled, and the incidence of the disorder was 0.67 cases per 100,000 children per year. Neonates were most commonly affected. Fifty-eight percent of the children had seizures, 76 percent had diffuse neurologic signs, and 42 percent had focal neurologic signs. Risk factors included head and neck disorders (in 29 percent), acute systemic illnesses (in 54 percent), chronic systemic diseases (in 36 percent), and prothrombotic states (in 41 percent). Venous infarcts occurred in 41 percent of the children. Fifty-three percent of the children received antithrombotic agents. Neurologic deficits were present in 38 percent of the children, and 8 percent died; half the deaths were due to sinovenous thrombosis. Predictors of adverse neurologic outcomes were seizures at presentation and venous infarcts. CONCLUSIONS: Sinovenous thrombosis in children affects primarily neonates and results in neurologic impairment or death in approximately half the cases. The occurrence of venous infarcts or seizures portends a poor outcome.     

Differentiated thyroid carcinomas with vascular invasion: a comparative study of follicular,Hürthle cell and papillary thyroid carcinoma

AIM: Non-medullary thyroid carcinomas arise from follicular cells. The purpose of this study is to correlate clinical and pathological properties of these tumours with the rate of distant metastasis from a series of thyroid tumours excised at one institution. METHODS: A total of 311 non-medullary thyroid tumours were identified and divided into: 29 follicular carcinoma (FC), 12 Hürthle cell carcinoma (HC), 13 Hürthle cell papillary thyroid carcinoma (HPTC) with vascular invasion (VI), 32 papillary thyroid carcinoma (PTC) with VI and 225 PTC without VI. The mean follow-up was 6.5 years with a range of 1-17 years. The tumours were histologically subdivided into minimal or wide invasion for FC and HC and focal or extensive invasion for PTC and HPTC, and stratified according to status of VI. RESULTS: The rate of distant metastasis was similar for FC, malignant Hürthle cell tumours and PTC with VI, and increased with extent of invasion. VI was seen in 12% of all PTC and 0% of HPTC in this study. PTC without VI were associated with a much lower potential of distant metastasis, were smaller in size and occurred in patients of younger age than PTC with VI. In addition, there was a tendency for increased potential for distant metastases with increased tumour size and patient age for all groups of tumours in the study. Patient age and tumour size appeared to play a smaller role than that of VI in predicting distant metastasis. CONCLUSIONS: Our study suggests that the rate of distant metastasis relates to VI, patient age and tumour size, regardless of Hürthle cell, FC or PTC differentiation. PTC of large size, and in patients older than 45 years, have a high propensity for vascular invasion.     

婴幼儿外部性脑积水与热性惊厥关系初探

目的：探讨婴幼儿外部性脑积水(EH)与热性惊厥(FC)的相关关系。方法：采用前瞻性多中心研究方法。对193例出生后3个月时出现EH的患儿进行追踪研究，观察其发生FC的情况并与对照组比较。结果：观察组共有167例患儿，对照组共有152例儿童完成研究。两组间在6个月、1岁、2岁、3岁时FC发病累积例数分别为3例(1．80％)、11例(6．57％)、21例(12．17％)、27例(16．17％)和1例（0．66％)、3例(1．32％)、5例(3．28％)、6例(3．95％)，两组间累积患病率的比较差异有显著意义。结论：EH患儿的FC发病率显著高于对照组，EH应认为是FC发病的重要病理基础之一。     

Resistance of broiler outbred lines to infection with Salmonella enteritidis

Salmonella infections originating from poultry are one of the major causes of food-borne disease. For the control of salmonella in poultry a multifactorial approach is more likely to be effective, and the genetic resistance of poultry breeds to salmonella infections may be a valuable contribution. Experimental Salmonella enteritidis infections were examined in three different broiler outbred lines: the FC line, which had been selected for feed conversion efficiency; the R line, which had been selected for growth rate; and the C line, a commercially available line. The FC line had the highest mortality rate after intramuscular inoculation with 5 × 10 6 colony forming units (CFU) of S. enteritidis at 2 weeks of age (40% versus 21 and 20% in the other lines). However, at slaughter age, the number of birds carrying salmonella in caecal contents, and the concentration of salmonella in the caecal contents, was lowest in the FC line. The FC and R lines were compared by inoculation with doses ranging from 10 2 to 10 7 CFU S. enteritidis . At sublethal doses (10 5 CFU or less), the FC line carried significantly less salmonella in caecal contents and the rate of systemic infection was lower. The start of shedding was also delayed compared with the R line. At doses of 10 6 CFU S. enteritidis or higher, there were no differences in salmonella carriage between the lines, and the FC line showed higher mortality. In conclusion, resistance to mortality and resistance to the carriage of S. enteritidis do not necessarily coincide within lines, as the FC line showed high mortality but low carriage, both in survivors of high infection doses and in all birds at lower infection doses.