Hemoglobin oxygen saturation discrepancy using various methods in patients with sickle cell vaso-occlusive painful crisis

OBJECTIVE: To evaluate agreement among various methods for measuring oxyhemoglobin (O2Hb) saturation in adult hypoxic patients with sickle cell disease (SCD) during painful vaso-occlusive crisis and to compare those results with a control group. PATIENTS AND METHODS: The hemoglobin oxygen saturation was determined simultaneously by pulse oximetry (SpO2), co-oximetry [SO2 (functional oxyhemoglobin saturation) and FO2Hb (oxyhemoglobin fraction)] and by calculation (SaO2) using a normal O2Hb dissociation curve in 18 adult patients with SCD during vaso-occlusive crisis and 12 non-SCD patients with various cardiopulmonary diagnoses. The method proposed by Bland and Altman was used to evaluate agreement of various methods in each of the two groups. RESULTS: Mean differences between various methods in patients with SCD were significantly larger than the control group. Limits of agreement (LOA) were also wider in the SCD group than in the control group. Mean bias between SpO2 and SO2, and SpO2 and FO2Hb in patients with SCD were -3.1 +/- 4.4 (LOA: -11.9 to 5.7) and 2 +/- 4.1 (LOA: -6.2 to 10.2) respectively, compared with -1.4 +/- 1.4 (LOA: -4.2 to 1.4) and 1.2 +/- 1.5 (LOA: -1.9 to 4.3) in the control group. A mean bias of -4.5 +/- 4 (LOA: -12.5 to 3.5) between SpO2 and SaO2 was noted in patients with SCD compared with -0.1 +/- 2.1 (LOA: -4.3 to 4.1) in the control group. The width of LOA for various methods in patients with SCD ranged from 9.8 to 17.6 compared with 1.3 to 8.4 in the control group. CONCLUSION: Patients with SCD during vaso-occlusive crisis have discrepancies in O2Hb saturation measurements by various methods. Abnormal pulse oximetry values in these patients should be interpreted cautiously and supplemented by arterial blood gas analysis and co-oximetry.     

Sickle cell acute chest syndrome: pathogenesis and rationale for treatment.

Acute chest syndrome (ACS) is a leading cause of death in sickle cell disease (SCD). Our previous work showed that hypoxia enhances the ability of sickle erythrocytes to adhere to human microvessel endothelium via interaction between very late activation antigen-4 (VLA4) expressed on sickle erythrocytes and the endothelial adhesion molecule vascular cell adhesion molecule-1 (VCAM-1). Additionally, hypoxia has been shown to decrease the production of nitric oxide (NO) which inhibits VCAM-1 upregulation. Based on these observations, we hypothesize that during ACS, the rapidly progressive clinical course that can occur is caused by initial hypoxia-induced pulmonary endothelial VCAM-1 upregulation that is not counterbalanced by production of cytoprotective mediators, including NO, resulting in intrapulmonary adhesion. We assessed plasma NO metabolites and soluble VCAM-1 in 36 patients with SCD and 23 age-matched controls. Patients with SCD were evaluated at baseline (n = 36), in vaso-occlusive crisis (VOC; n = 12), and during ACS (n = 7). We observed marked upregulation of VCAM-1 during ACS (1,290 +/- 451 ng per mL; mean +/- 1 SD) with values significantly higher than controls (P <.0001) or patients either in steady state or VOC (P <. 01). NO metabolites were concomitantly decreased during ACS (9.2 +/- 1.5 nmol/mL) with values lower than controls (22.2 +/- 5.5), patients during steady state (21.4 +/- 5.5), or VOC (14.2 +/- 1.2) (P <.0001). Additionally, the ratio of soluble VCAM-1 to NO metabolites during ACS (132.9 +/- 46.5) was significantly higher when compared with controls (P <.0001) or patients either in steady state or VOC (P <.0001). Although hypoxia enhanced in vitro sickle erythrocyte-pulmonary microvessel adhesion, NO donors inhibited this process with concomitant inhibition of VCAM-1. We suggest that in ACS there is pathologic over expression of endothelial VCAM-1. Our investigations also provide a rationale for the therapeutic use in ACS of cytoprotective modulators including NO and dexamethasone, which potentially exert their efficacy by an inhibitory effect on VCAM-1 and concomitant inhibition of sickle erythrocyte-endothelial adhesion.     

Elevated serum and bronchoalveolar lavage fluid levels of interleukin 8 and granulocyte colony-stimulating factor associated with the acute chest syndrome in patients with sickle cell disease

The role of cytokines in the development of acute chest syndrome (ACS) in patients with sickle cell disease (SCD) was studied. Serum interleukin 8 (IL-8) levels were elevated in 14 episodes and undetectable in six out of 20 episodes of ACS in 19 patients with SCD. In contrast, IL-8 levels were undetectable in the sera of 29 control patients with SCD studied during routine clinic visits or hospitalization for vaso-occlusive crises. The differences in mean IL-8 levels and the proportion of patients with detectable levels between the two groups were highly significant (P < 0.0001 and 0.04 respectively). The mean IL-8 level in bronchial fluid samples from children with ACS was also significantly higher than that in sickle cell patients undergoing elective surgery (5500 +/- 1400 pg/ml vs. 1900 +/- 470 pg/ml, P = 0.03). Granulocyte colony-stimulating factor (G-CSF) (2000 +/- 1700 pg/ml) was present in five out of six samples of bronchial fluid, but not serum, from children with ACS. All but one of the patients with ACS studied were negative for the Duffy red cell antigen, which is a receptor that binds and inactivates IL-8 and other chemokines. These findings suggest that IL-8 and G-CSF may play a role in the development of the ACS and the complications associated with it.     

Increased levels of soluble ICAM-1 in the plasma of sickle cell patients are reversed by hydroxyurea

Increased adhesive events between the blood vessel endothelium and red and white cells play a central role in the initiation of vasoocclusive crisis in sickle cell disease (SCD). Soluble VCAM-1 levels are increased in the plasma of sickle cell patients and may be reduced during hydroxyurea (HU) therapy. Reports regarding any changes in soluble ICAM-1 (sICAM-1) levels in sickle cell patients, however, are conflicting, and as yet no beneficial effect of HU upon levels has been observed. Thus, we sought to thoroughly investigate changes in sICAM-1 levels in SCD patients and the effect of HU therapy (20-30 mg/kg/day). Plasma sVCAM-1 levels were significantly higher in steady-state SCD patients than in normal controls (766 +/- 86 ng/mL vs. 325 +/- 38 ng/mL, respectively, P < 0.0001). sVCAM-1 levels were decreased in patients on HU therapy (543 +/- 69 ng/mL) compared to those not taking HU; however, this difference was not significant. Plasma sICAM-1 levels were significantly increased in steady-state SCD patients compared to normal individuals (285 +/- 20 ng/mL vs. 202 +/- 16 ng/mL, respectively, P = 0.002), and HU therapy significantly reduced sICAM-1 levels in patients (217 +/- 12, P = 0.027) to levels approaching those of healthy individuals. sVCAM-1 levels inversely correlated with fetal hemoglobin levels in SCD patients, while a nonsignificant inverse trend was observed between sICAM-1 levels and fetal hemoglobin. In conclusion, plasma sICAM-1 levels were significantly increased in SCD patients, and this increase was reversed by hydroxyurea therapy, possibly reflecting reduced endothelial activation in patients taking HU. Such an event may benefit patients by reducing adhesive interactions between white cells and the endothelium.     

Secretory phospholipase A(2) predicts impending acute chest syndrome in sickle cell disease

Acute chest syndrome (ACS) is the leading cause of death in sickle cell disease. Severe ACS often develops in the course of a vaso-occlusive crisis (VOC), but currently there are no predictors for its development. Secretory phospholipase A(2) (sPLA(2)), a potent inflammatory mediator, is elevated in ACS, and previous work suggests that sPLA(2) predicts impending ACS. We prospectively evaluated sPLA(2) concentration during 21 admissions for VOC; 6 of these patients went on to develop ACS. Elevation of sPLA(2) was detected all 6 patients 24 to 48 hours before ACS was clinically diagnosed. Adding the requirement for fever raised the specificity of sPLA(2) to 87% while retaining 100% sensitivity. These data indicate that sPLA(2) can be useful in alerting the clinician to patients with impending ACS. In addition, sPLA(2) may be useful for instituting early therapies to prevent or reduce the clinical morbidity of ACS.     

Vasoactive factors in sickle cell disease: in vitro evidence for endothelin-1-mediated vasoconstriction

While systemic plasma endothelin-1 (ET-1) levels are increased during acute crisis in sickle cell disease, the relative levels of potent vasoactive factors that contribute to the regulation of vascular function, such as ET-1, NO, and cell-free hemoglobin, during the course of periodic vaso-occlusive episodes remain unclear. Moreover, whether and to what extent sickling-induced release of ET-1 alters vascular tone is not completely understood. To investigate the sequential changes in circulating vasoactive factors, we measured plasma ET-1, NO metabolites (NOx), and cell-free hemoglobin (Hb) before (steady-state), during (crisis), and after a vaso-occlusive (post-crisis) episode. Steady-state ET-1 levels (fmol/mL) increased from 2.3 +/- 0.4 to 11.0 +/- 1.4 and 4.2 +/- 1.0 during crisis and post-crisis periods, respectively. There was no significant difference in plasma NOx levels. Cell-free Hb levels were significantly higher in sickle cell patients in all phases as compared to the control group, and especially during crisis cell-free Hb levels were elevated by 4-fold (209,000 +/- 31,000 vs. 46,000 +/- 5,300 ng/mL in steady-state). Conditioned medium from human pulmonary artery endothelial cells exposed to sickled erythrocytes prepared by deoxygenation induced contraction of aortic rings, and this effect was blocked by an ET(A) receptor antagonist. These findings indicate that ET-1 is the predominant contractile factor released by cultured endothelial cells upon exposure to deoxygenated sickled SS erythrocytes and ET-1-NO-NO scavenger balance is altered in favor of vasoconstriction during an acute episode in SCD.     

Acute chest syndrome in adults with sickle cell disease

STUDY OBJECTIVES: Acute chest syndrome (ACS) is a frequent and potentially severe pulmonary illness in sickle cell disease (SCD). The aim of the study was to report the clinical features and outcome of consecutive ACS episodes in adult patients in a French SCD center. All patients were treated according to an uniform therapeutic protocol applying transfusion only in the more severe clinical form of ACS. RESULTS: There were 107 consecutive episodes in 77 adult patients (mean age, 29 +/- 7 years; 78% hemoglobin [Hb] SS; 14% Hb SC; and 8% Hb Sbeta + thalassemia) over a 6-year period. Seventy-eight percent of our patients had an associated vaso-occlusive crisis that preceded the chest signs in half of the cases. Comparison between acute and baseline levels showed a statistically significant difference in Hb levels (drop of 1.6 to 2. 25 g/dL depending on Hb genotype), WBC count (increase of 9.2 +/- 8. 3 x 10(9)/L); platelet count (increase of 67 +/- 209 x 10(9)/L); and lactate dehydrogenase values (increase of 358 +/- 775 IU/L) in ACS patients. Hypercapnia was detected in 42% of patients without sign of narcotic abuse. We identified a high percentage of alveolar macrophages containing fat droplets in 31 of 43 (77%) patients who underwent BAL. Bacterial culture findings were almost always negative, but were performed after starting antibiotic therapy that was administered in 96 episodes. Transfusion was required in 50 of 107 ACS events (47%). Five patients died, and all were transfused. CONCLUSIONS: These results confirm that fat embolism is probably a frequent mechanism of ACS in adult patients. However, fat embolism was not associated with a more severe clinical course, suggesting that bronchoscopy and BAL have little impact on the management of these patients. Restricting transfusion to the most severe ACS cases does not seem to increase the mortality rate.     

Cytokine profile of sickle cell disease in Oman

The aim of our study was to assess the cytokine profile of sickle cell disease (SCD) patients in steady state and in vaso-occlusive crisis (VOC). VOC has a complex nature, involving interactions between sickle red blood cells (RBC), the endothelium, and leucocytes. Endothelial damage due to recurrent adhesion of sickle RBCs may disrupt endothelial function, leading to altered cytokine release. It is therefore pertinent to study the cytokine profile of SCD patients in steady state and in crisis prior to exploring its contribution to vaso-occlusive manifestations, since it is believed that an altered balance of proinflammatory and anti-inflammatory cytokines plays an important role in painful crisis. Cytokines including IL-1beta, IL-2, IL-4, IL-6, IL-8, TNF-alpha, and IFN-gamma were measured by commercially available ELISA kits in SCD patients (n = 60); in steady state (n = 26) and in painful crisis (n = 34) and compared with nonanemic age- and sex-matched normal Omani controls (n = 20). SCD patients in crisis showed elevated levels of TNF-alpha (P < 0.092) and IL-6 (P < 0.024) when compared with steady state. It was also observed that SCD patients in steady state showed a significant elevation in IL-1beta (P < 0.04), IL-6 (P < 0.0001), and IFN-gamma (P < 0.02) as compared to normal subjects. It is thus evident that both type I and type II cytokines are significantly altered in SCD patients. In steady state, type II proinflammatory cytokines are elevated, whereas in crisis, an additional augmentation of type I cytokines occurs, with persistent elevation of type II cytokines, emphasizing the role of perturbed endothelium and activated monocytes in the pathophysiology of vaso-occlusion in sickle cell crisis.     

Placenta growth factor activates monocytes and correlates with sickle cell disease severity

Sickle cell disease (SCD) results in chronic hypoxia and secondarily increased erythropoietin concentrations. Leukocytosis and activated monocytes are also observed in SCD in absence of infection or vaso-occlusion (steady state), the reasons for which are unknown. We found that erythroid cells produced placenta growth factor (PlGF), an angiogenic growth factor belonging to the vascular endothelial growth factor (VEGF) family, and its expression was induced in bone marrow CD34+ progenitor cells in the presence of erythropoietin. Furthermore, the steady state circulating PlGF levels in subjects with severe SCD (at least 3 vaso-occlusive crises [VOCs] per year) were 18.5 +/- 1.2 pg/mL (n = 9) compared with 15.5 +/- 1.2 pg/mL (n = 13) in those with mild SCD (fewer than 3 VOCs per year) and 11.3 +/- 0.7 pg/mL (n = 9) in healthy controls (P <.05), suggesting a correlation between PlGF levels and SCD severity. In addition, PlGF significantly increased mRNA levels of the proinflammatory cytochemokines interleukin-1beta, interleukin-8, monocyte chemoattractant protein-1, and VEGF in peripheral blood mononuclear cells (MNCs) of healthy subjects (n = 4; P <.05). Expression of these same cytochemokines was significantly increased in MNCs from subjects with SCD at steady state (n = 14), compared with healthy controls. Of the leukocyte subfractions, PlGF stimulated monocyte chemotaxis (P <.05, n = 3). Taken together, these data show for the first time that erythroid cells intrinsically release a factor that can directly activate monocytes to increase inflammation. The baseline inflammation seen in SCD has always been attributed to sequelae secondary to the sickling phenomenon. We show that PlGF contributes to the inflammation observed in SCD and increases the incidence of vaso-occlusive events.     

C-reactive protein, interleukin-6, secretory phospholipase A2 group IIA and intercellular adhesion molecule-1 in the prediction of late outcome events after acute coronary syndromes

OBJECTIVE: We investigated whether levels of C-reactive protein (CRP), interleukin-6 (IL-6), secretory phospholipase A(2) group IIA (sPLA(2)-IIA) and intercellular adhesion molecule-1 (ICAM-I) predict late outcomes in patients with acute coronary syndromes (ACS). DESIGN: Prospective longitudinal study. CRP (mg L(-1)), IL-6 (pg mL(-1)), sPLA(2)-IIA (ng mL(-1)) and ICAM-1 (ng mL(-1)) were measured at days 1 (n = 757) and 4 (n = 533) after hospital admission for ACS. Their relations to mortality and rehospitalization for myocardial infarction (MI) and congestive heart failure (CHF) were determined. SETTING: Coronary Care Unit at Sahlgrenska University Hospital, Gothenburg, Sweden. SUBJECTS: Patients with ACS alive at day 30; median follow-up 75 months. RESULTS: Survival was related to day 1 levels of all markers. After adjustment for confounders, CRP, IL-6 and ICAM-1, but not sPLA(2)-IIA, independently predicted mortality and rehospitalization for CHF. For CRP, the hazard ratio (HR) was 1.3 for mortality (95% confidence interval (CI): 1.1-1.5, P = 0.003) and 1.4 for CHF (95% CI: 1.1-1.9, P = 0.006). For IL-6, HR was 1.3 for mortality (95% CI: 1.1-1.6, P < 0.001) and 1.4 for CHF (95% CI: 1.1-1.8, P = 0.02). For ICAM-1, HR was 1.2 for mortality (95% CI: 1.0-1.4, P = 0.04) and 1.3 for CHF (95% CI: 1.0-1.7, P = 0.03). No marker predicted MI. Marker levels on day 4 provided no additional predictive value. CONCLUSIONS: In patients with ACS, CRP, IL-6, sPLA(2)-IIA and ICAM-1 are associated with long-term mortality and CHF, but not reinfarction. CRP, IL-6 and ICAM-1 provide prognostic information beyond that obtained by clinical variables.     

Patient-controlled analgesia versus continuous infusion of morphine during vaso-occlusive crisis in sickle cell disease, a randomized controlled trial

Intravenous morphine is the treatment of choice for severe pain during vaso- occlusive crisis in sickle cell disease (SCD). However, side effects of morphine may hamper effective treatment, and high plasma levels of morphine are associated with severe complications such as acute chest syndrome. Furthermore, adequate dosing remains a problem since no objective measurement of pain severity exists and analgesia should be titrated upon the patient's reported pain. Patient-controlled analgesia (PCA) may therefore be an interesting alternative since patients can titrate the level of analgesia themselves. In this randomized controlled study, the efficacy of intravenous morphine administration with PCA was compared with continuous infusion (CI) of morphine in patients with SCD during vaso-occlusive crisis. Twenty five consecutive episodes of vaso-occlusive crisis in 19 patients with SCD were included in the study. Patients in the PCA-group had a markedly and significant lower mean and cumulative morphine consumption when compared with the patients in the CI-group (0.5 mg/hr versus 2.4 mg/hr (P < 0.001) and 33 mg versus 260 mg (P = 0.018, respectively). The mean daily pain scores were comparable (4.9 versus 5.3). The lower mean and cumulative morphine consumption in the PCA-group led to significant less nausea and constipation during treatment when compared with the CI-group (area under the curve, respectively, 11 versus 18 (P = 0.045) and 30 versus 45 (P = 0.021). Furthermore, a nonsignificant reduction in the duration of hospital admission of 3 days was observed in the PCA-group. PCA results in adequate pain relief at a much lower morphine consumption and should considered to be the first choice in morphine administration to sickle cell patients admitted with vaso-occlusive crisis.     

Avascular necrosis of the hip in children with sickle cell disease and high Hb F: magnetic resonance imaging findings and influence of alpha-thalassemia trait

Avascular necrosis (AVN) of the hip is a common cause of morbidity in sickle cell disease (SCD). Its prevalence increases with age and predisposing factors include coexistent alpha-thalassemia trait, frequent vaso-occlusive crisis and a high hematocrit (Hct). SCD is relatively mild among Kuwaiti patients because of their elevated Hb F levels, but a subset exists with severe recurrent vaso-occlusive crises. We carried out a prospective magnetic resonance imaging (MRI) study of the hip in a group of patients being followed in the Pediatric Hematology clinics of Al-Mubarak and Al-Amiri Hospitals. The association of AVN with age, frequency of hospitalization, alpha-thal trait, steady-state Hb, Hct, Hb F, WBC and platelet counts was investigated. MRI was carried out with a 1.5-tesla GE unit with a super-conducting magnet. Thirty patients (19 males, 11 females) (23 SS and 7 SbetaThal) were studied. Their ages ranged from 6 to 17 years, with a mean of 9.8 +/- 3.5 years, and Hb F from 11 to 35% with a mean of 22.8 +/- 5.7%. Among the SS patients, 11 (47.8%) had coexistent alpha-thal trait (-3.7-kb deletion). A total of 8 (26.7%) patients (6 SS and 2 SbetaThal) had varying degrees of osteonecrosis of the hip. Four (36.4%) of the 11 SS patients with alpha-thal trait and 2 (16.7%) of those without alpha-thal trait had osteonecrosis. This difference is, however, not statistically significant (chi(2) = 0.3, p = 0.5). While there was also no significant difference in the mean age and hematological parameters (Hb, Hct, Hb F, WBC, platelets), the SS patients with osteonecrosis had a significantly higher number of hospitalizations for vaso-occlusive crisis in the preceding 3 years than those without osteonecrosis.     

冠心病患者分泌型磷脂酶A2的变化及其与白细胞介素8、溶血磷脂酸的关系

目的了解冠心病患者分泌型磷脂酶 A2(sPLA2)的变化,并通过测定 IL-8、LPA 等相关细胞因子,对 sPLA2的作用机制进行初步探讨。方法冠状动脉造影确诊的262例患者,其中急性冠脉综合征(ACS)110例,稳定性冠心病(SCHD)63例,正常患者89例,分别测定 sPLA2、白细胞介素8(IL-8)、高敏 C 反应蛋白(hs-CRP)和溶血磷脂酸(LPA)水平,并进行对比分析。结果冠心病患者sPLA2[(68±17)U/ml]、IL-8[(182±80)pg/ml]以及 LPA[(2.85±0.36)μmol/L]均明显高于对照组[sPLA2:(55±12)U/ml,IL-8:(119±33)pg/ml,LPA:(2.34±0.36)μmol/L,均 P<0.01],其中ACS 组的 sPLA2[(71±18)U/ml]、IL-8[(195±78)pg/ml]也明显高于 SCHD 组[sPLA2:(63±12)U/ml],IL-8:[(159±79)pg/ml,均 P<0.01;sPLA2与 IL-8(r=0.203,P=0.007)、LPA(r=0.658,P<0.01)、hs-CRP(r=0.231,P=0.005)均呈正相关;sPLA2≥63.75 U/ml 时,患冠心病的相对危险度为6.248(P<0.01)。结论冠心病患者 sPLA2明显升高,它可能与 IL-8共同参与冠心病的炎症发展过程,并与下游相关产物 LPA 进一步加速其进展。提示 sPLA2升高是冠心病的独立危险因素之一。     

Effect of low-dose warfarin on D-dimer levels during sickle cell vaso-occlusive crisis: a brief report

OBJECTIVE: To evaluate the activation of clotting systems in patients with sickle cell disease (SCD) by measuring the plasma D-dimer level and to determine the effect of low-dose warfarin on D-dimer level during vaso-occlusive crisis. METHODS: Plasma D-dimer level was measured in 65 blood samples of 37 adult patients with SCD who were hospitalized for vaso-occlusive painful crisis. D-dimer level of patients who were on low-dose warfarin was compared with those patients who were not on any anticoagulation treatment. Analysis of variance (anova) was carried out to determine factors significantly associated with low D-dimer level in patients with SCD. The following factors were included in the anova model; warfarin, homozygous hemoglobin S, history of blood transfusion in past 3 months, hydroxyurea, hemoglobin S%, hemoglobin F%, white blood cell counts, hemoglobin level, platelet count, and plasma fibrinogen level. RESULTS: Overall median D-dimer level in 65 samples was 2.7 microg fibrinogen equivalent units (FEU)/mL (0.34-4). Patients who were on low-dose warfarin had a median D-dimer level of 0.81 microg FEU/mL (0.34-1.8) compared with 3.1 microg FEU/mL (0.94-4) in those patients who were not on anticoagulation treatment. Using anova to model D-dimer levels, only warfarin was significantly correlated with low D-dimer levels after controlling for other variables. CONCLUSIONS: Patients with SCD during vaso-occulsive painful crisis have an elevated D-dimer level. Low-dose anticoagulation treatment is associated with a significant reduction in the D-dimer levels.     

Refining the value of secretory phospholipase A2 as a predictor of acute chest syndrome in sickle cell disease: results of a feasibility study (PROACTIVE)

Acute chest syndrome (ACS) is defined as fever, respiratory symptoms and a new pulmonary infiltrate in an individual with sickle cell disease (SCD). Nearly half of ACS episodes occur in SCD patients already hospitalized, potentially permitting pre-emptive therapy in high-risk patients. Simple transfusion of red blood cells may abort ACS if given to patients hospitalized for pain who develop fever and elevated levels of secretory phospholipase A2 (sPLA2). In a feasibility study (PROACTIVE; ClinicalTrials.gov NCT00951808), patients hospitalized for pain who developed fever and elevated sPLA2 were eligible for randomization to transfusion or observation; all others were enrolled in an observational arm. Of 237 enrolled, only 10 were randomized; one of the four to receive transfusion had delayed treatment. Of 233 subjects receiving standard care, 22 developed ACS. A threshold level of sPLA2 ≥ 48 ng/ml gave optimal sensitivity (73%), specificity (71%) and accuracy (71%), but a positive predictive value of only 24%. The predictive value of sPLA2 was improved in adults and patients with chest or back pain, lower haemoglobin concentration and higher white blood cell counts, and in those receiving less than two-thirds maintenance fluids. The hurdles identified in PROACTIVE should facilitate design of a larger, definitive, phase 3 randomized controlled trial.     

Individual red blood cell fetal hemoglobin quantification allows to determine protective thresholds in sickle cell disease

Polymerization of the sickle hemoglobin (HbS) is a key determinant of sickle cell disease (SCD), an inherited blood disorder. Fetal hemoglobin (HbF) is a major modulator of the disease severity by both decreasing HbS intracellular concentration and inhibiting its polymerization. However, heterocellular distribution of HbF is common in SCD. For HbS polymerization inhibition, the hypothesis of an “HbF per red blood cell (HbF/RBC) threshold” requires accurate measurement of HbF in individual RBC. To date, HbF detection methods are limited to a qualitative measurement of RBC populations containing HbF - the F cells, which are variable. We developed an accurate method for HbF quantification in individual RBC. A linear association between mean HbF content and mean RBC fluorescence by flow cytometry, using an anti-Human-HbF antibody, was obtained from non-SCD subjects presenting homogeneous HbF distribution. This correlation was then used to measure HbF/RBC. Hydroxyurea (HU) improves SCD clinical manifestations, mainly through its ability to induce HbF synthesis. The HbF distribution was analyzed in 14 SCD patients before and during HU treatment. A significant decrease in RBC population containing less than 2 pg of HbF/RBC was observed. Therefore, we tested associations for %RBC above different HbF/RBC thresholds and showed a decrease in the pathognomonic vaso-occlusive crisis incidence from the threshold of 4 pg. This quantity was also correlated with the level of sickle RBC after in vitro deoxygenation. This new method allows the comparison of HbF/RBC distributions and could be a useful tool to characterize baseline patients HbF distribution and therapeutic response to HbF inducers.     

Cost-effectiveness of adenotonsillectomy in reducing obstructive sleep apnea,cerebrovascular ischemia,vaso-occlusive pain,and ACS episodes in pediatric sickle cell disease

In children with sickle cell disease (SCD), adenotonsillar hypertrophy or recurrent tonsillitis are frequently linked with an increased risk of obstructive sleep apnea, cerebrovascular ischemia, or frequent pain episodes and often require an adenoidectomy and/or tonsillectomy. Interventions designed to prevent these complications, control vaso-occlusive pain episodes, and avoid hospitalizations may reduce the significant personal and economic burden of SCD. This study compares episode recurrence and treatment costs for cerebrovascular ischemia, vaso-occlusive pain, acute chest syndrome (ACS), and obstructive sleep apnea in children who had an adenotonsillectomy (A/T surgery, N = 256; 11.7%) and a matched cohort of those who did not (N = 512; 23.3%) from a cohort of 2,194 children and adolescents with SCD from South Carolina’s Medicaid system. A/T surgery was associated with a significantly reduced rate of visits over time for obstructive sleep apnea and cerebrovascular ischemia (e.g., stroke, transient ischemic attacks), but not with any change in the rate of visits for vaso-occlusive pain or ACS/pneumonia visits. The rate of mean acute (emergency and inpatient) service costs was significantly decreasing over time after an increase about the time the A/T surgery was performed. The cost-effectiveness of adenoidectomy and/or tonsillectomy for treating obstructive sleep apnea and preventing cerebrovascular ischemia without increasing vaso-occlusive pain episodes or long-term acute service costs in routine clinical practice settings was demonstrated. The matched control group of SCD patients without A/T surgery contained more patients with severe vaso-occlusive pain episodes, ACS visits, and higher mean total costs over time and appears to represent a different phenotype of children with SCD.     

Microvascular abnormalities in sickle cell disease: a computer-assisted intravital microscopy study

The conjunctival microcirculation of 18 homozygous sickle cell disease (SCD) patients during steady-state, painful crisis, and postcrisis conditions was recorded on high-resolution videotapes using intravital microscopy. Selected videotape sequences were subsequently coded, frame-captured, studied, and blindly analyzed using computer-assisted image analysis protocols. At steady-state (baseline), all SCD patients exhibited some of the following morphometric abnormalities: abnormal vessel diameter, comma signs, blood sludging, boxcar blood flow phenomenon, distended vessels, damaged vessels, hemosiderin deposits, vessel tortuosity, and microaneurysms. There was a decrease in vascularity (diminished presence of conjunctival vessels) in SCD patients compared with non-SCD controls, giving the bulbar conjunctiva a "blanched" avascular appearance in most but not all SCD patients during steady-state. Averaged steady-state red cell velocity in SCD patients was slower than in non-SCD controls. During painful crisis, a further decrease in vascularity (caused by flow stoppage in small vessels) and a 36.7% +/- 5.2% decrease in large vessel (mostly venular) diameter resulted. In addition, the conjunctival red cell velocities either slowed significantly (6.6% +/- 13.1%; P <.01) or were reduced to a trickle (unmeasurable) during crisis. The microvascular changes observed during crisis were transient and reverted to steady-state baseline after resolution of crisis. When combined, intravital microscopy and computer-assisted image analysis (computer-assisted intravital microscopy) represent the availability of a noninvasive tool to quantify microvascular abnormalities in vascular diseases, including sickle cell disease. The ability to identify and relocate the same conjunctival vessels for longitudinal studies uniquely underscores the applicability of this quantitative real-time technology.     

Arginine therapy: a novel strategy to induce nitric oxide production in sickle cell disease

To determine the effects of L-arginine (L-Arg) supplementation on nitric oxide metabolite (NOx) production, oral L-Arg was given to normal controls, sickle cell disease (SCD) patients at steady state and SCD patients hospitalized with a vaso-occlusive crisis (VOC). L-Arg (0.1 g/kg) increased NOx formation by 18.8 +/- 68% in normal controls, whereas steady-state SCD patients demonstrated a paradoxical decrease in NOx of -16.7 +/- 4% (P = 0.004). In contrast, patients with VOC demonstrated a dramatic increase in NOx production by +77.7 +/- 103%, a response that was dose dependent. L-Arg appears to be the rate-limiting step in NOx production during VOC. Oral arginine may therefore benefit SCD patients by inducing an increase in NO production during VOC.     

Plasma d-dimer levels increase with the severity of community acquired pneumonia

The aim of this study is to investigate the relationship of the plasma D-Dimer (D-d) level and the severity of the pneumonia in patients who have not any disease that may increase the D-d level, but pneumonia. This is prospective controlled study. Using the ATS 2001 Community Acquired Pneumonia (CAP) Guideline we divided the patients into two groups [severe (n= 14) and non-severe (n= 37) CAP] and looked for any significant difference in D-d levels with ELISA method among the patients groups and control group. Plasma D-d levels were 2438 +/- 2158 ng/mL in severe CAP group, 912.6 +/- 512.6 ng/mL in non-severe CAP group and 387 +/- 99.56 ng/mL in the control group. Patients with non-severe CAP and those with severe CAP group both showed an increase in plasma levels of D-d compared to control group (p< 0.05, p< 0.001, respectively). We also found that the severe CAP group had increased in plasma levels of D-d compared to the non-severe CAP group (p< 0.001). Plasma D-d level increases significantly in patients with CAP compared to control group. Plasma D-d levels increases significantly with the severity of the CAP.