Detection of antibodies to Trypanosoma cruzi among blood donors in the southwestern and western United States. II. Evaluation of a supplemental enzyme immunoassay and radioimmunoprecipitation assay for confirmation of seroreactivity

BACKGROUND: Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi, is endemic to Latin America and may be transmitted in the United States via blood donated by infected immigrants. Blood- borne pathogens such as T. cruzi require supplemental testing for confirmation of seroreactivity. STUDY DESIGN AND METHODS: A study was undertaken to determine an optimal scheme for confirmation of seroreactivity in repeatedly reactive samples identified by the Chagas antibody enzyme immunoassay (EIA). The procedure for initial confirmation involves three purified antigens coated onto three separate polystyrene beads and uses an EIA format. If the sample is reactive with two of three or three of three antigens, it is confirmed as seroreactive. If none or one of three beads is reactive, the sample is indeterminate and subjected to a radioimmunoprecipitation assay (RIPA). The RIPA must demonstrate characteristic bands at 32, 34, and 90 kDa. RESULTS: When tested with sera from persons with potentially cross-reactive diseases (n = 39) or against a presumed negative population from southeast Wisconsin (n = 289), the confirmatory EIA had a specificity of 100 percent. Sensitivity was 100 percent (28/28) with xenodiagnosis-positive sera and 97.6 percent (80/82) with chagasic sera from Latin America. The RIPA showed a specificity of 100 percent in EIA- nonreactive samples (n = 100) and a sensitivity of 100 percent with both xenodiagnosis-positive (28/28) and chagasic (82/82) sera. CONCLUSION: The confirmatory EIA and the RIPA together provide a highly specific and sensitive means of confirming seroreactivity for antibodies to T. cruzi.     

Gastric Status and Vitamin B12 Levels in Cardiovascular Patients

Proper absorption of vitamin B12 requires gastric corpus mucosa that functions appropriately and secretes intrinsic factor needed as an essential cofactor for the absorption of dietary vitamin B12 in the small bowel. Here we describe the prevalence of vitamin B12 deficiency and atrophic corpus gastritis (ACG) in patients with coronary heart disease. Fasting serum was obtained from patients who were admitted for cardiovascular diseases at the Coronary Care Unit in Nijmegen, the Netherlands. The status of gastric mucosa was assessed by using the serum levels of pepsinogens I and II, gastrin-17, and Helicobacter pylori IgG antibodies and analyzed over vitamin B12 level subgroups. The study population consisted of 376 patients (mean age, 65 years [SD, 13 years], 227 [60%] males). Low vitamin B12 levels (<150 pM) were detected in 28 patients (7%). Of these 28 patients, 5 (18%) had ACG according to the biomarker assays. Altogether, another 140 patients (37%) had vitamin B12 levels between 150 and 250 pM, of whom 10 (7%) had ACG. Of the remaining patients, five (2%) had ACG. Deficiency of vitamin B12 is common among subjects with coronary heart disease. Up to 20% of these deficiencies are related to ACG. Professor Pentti Sipponen is scientific advisor for Biohit Plc, the company that developed the H. pylori, serum pepsinogen, and gastrin-17 assays.     

Long-term results of endovascular abdominal aortic aneurysm treatment with the first generation of commercially available stent grafts

HYPOTHESIS: Little information about the long-term results of endovascular abdominal aortic aneurysm repair is available. This study was performed to evaluate the long-term data of patients treated with the first generation of commercially available stent grafts. DESIGN: Multicenter registry. SETTING: Sixty-two European centers that participated in the EUROSTAR (EUROpean collaborators on Stent-graft Techniques for abdominal aortic Aneurysm Repair) registry. PATIENTS: A total of 1190 patients with a follow-up of up to 8 years, who underwent endovascular abdominal aortic aneurysm repair with a stent graft (Stentor or Vanguard). INTERVENTION: Elective endovascular abdominal aortic aneurysm repair. MAIN OUTCOME MEASURES: The morbidity and mortality data of patients treated with the first-generation stent graft who enrolled in the EUROSTAR registry were analyzed. Incidence rates of complications were calculated to quantify annual risks. Life-table analyses and multivariate Cox proportional hazards models were used for the survival analysis. RESULTS: Conversion to open repair, aneurysm rupture, all-cause death, and aneurysm-related death occurred in 7.1%, 2.4%, 19.9%, and 3.0% of the patients, respectively. The cumulative percentage of the combined outcome event, conversion-free and rupture-free survival, after 8 years was 48.0%. Procedure-related complications that frequently occurred were endoleak (13.0 cases per 100 patient-years), stenosis/thrombosis (4.6 cases per 100 patient-years), and stent migration (4.3 cases per 100 patient-years). CONCLUSIONS: Patients treated with the first generation of stent grafts will need lifelong surveillance because of a considerable risk of late complications. How these findings translate to the outcome of newer-generation stent grafts is unknown. For this reason, vigilant surveillance remains indicated in all patients who undergo endovascular abdominal aortic aneurysm repair.     

Adding familial risk assessment to faecal occult blood test can increase the effectiveness of population-based colorectal cancer screening

Background

The Dutch Health Council recently recommended the introduction of a colorectal cancer (CRC) screening programme by faecal occult blood testing (FOBT) for individuals aged 55-75 at population risk of CRC. Individuals at an increased familial CRC risk (?2 times population risk) should be identified at a younger age, so they and their relatives can receive earlier, more intensive surveillance instead of FOBT.

Aims

To determine the percentage of participants with a positive FOBT in a CRC screening programme with an increased familial CRC risk.

Methods

In a population-based study, 10,569 individuals aged 50-75 received an FOBT. Individuals with a positive FOBT were invited for colonoscopy and familial risk assessment. Participants with an average familial CRC risk were compared to those with an increased risk. Increased familial CRC risk was defined as a cumulative lifetime risk of CRC of at least 10%.

Results

Of 6001 participants, 430 had a positive FOBT, of whom 324 (63% males; mean age 63 years) completed colonoscopy and familial risk assessment. CRC (n = 22) and/or advanced adenomas (n = 122) were found in 133 participants. Familial CRC risk was increased in 6% of participants with a positive FOBT. No significant differences were found between participants with an average versus an increased familial CRC risk.

Conclusion

Six percent of participants with a positive FOBT had an increased familial CRC risk. Identifying at-risk participants enables them and their relatives to undergo regular colonoscopies. Adding familial risk assessment to FOBT screening may thus prevent a substantial number of CRCs.     

Hyperhomocysteinaemia and vitamin B12 deficiency: the long-term effects in cardiovascular disease

BACKGROUND: An elevated plasma homocysteine level is an established risk factor for cardiovascular disease. Vitamin B12 plays a key role in homocysteine metabolism and could be the main factor in causing cardiovascular disease as well. OBJECTIVES: The aim of this study was to assess whether vitamin B12 deficiency or hyperhomocysteinaemia is associated with recurrent cardiovascular events. METHODS: Overall, 211 patients discharged alive from our Coronary Care Unit were recruited from February till May 1998. Serum vitamin B12 and plasma homocysteine levels were measured in fasting blood samples. Patient characteristics, medical information and cardiovascular risk factors were assessed from medical files. Patients were followed for 5 years and the prevalence of cardiovascular mortality and morbidity was collected. RESULTS: In the follow-up period of 810 person-years, 48 (21%) of the patients experienced a nonfatal recurrent cardiovascular event and another 14 (7%) died of a cardiovascular cause. Among those with ischaemic heart disease at discharge, no difference in survival was found between the patients with a low (<250 pmol/l) or a high vitamin B12 level (p = 0.21). In patients with hyperhomocysteinaemia (>16 micromol/l), an increased risk of a recurrent cardio vascular event (p = 0.05) in comparison to those with normal plasma homocysteine levels was proven (adjusted hazard ratio of 2.22 (95% CI: 1.40-3.04). CONCLUSIONS: In conclusion, high plasma homocysteine concentration, but not a low serum vitamin B12 concentration, increases the risk of cardiovascular morbidity and mortality in patients with ischaemic heart disease.     

The factor V B-domain provides two functions to facilitate thrombin cleavage and release of the light chain

Blood coagulation factors V and VIII are homologous proteins that have the domain organization A1-A2-B-A3-C1-C2. Upon thrombin activation, the B-domains of both molecules are released. Previous studies on factor VIII showed that the B-domain was not required for thrombin cleavage or activity. In contrast, deletion of the factor V B-domain (residues 709 to 1545) yielded a molecule with sevenfold reduced procoagulant activity that was not cleaved by thrombin. However, this factor V B- domain deletion molecule was activated by factor Xa, although the fold- activation was 85% that of wild-type factor V. Thrombin cleavage of factor V occurs initially after residue 709 and subsequently after residues 1018 and 1545. The requirement for thrombin cleavage within the B-domain at residue 1018 was evaluated by mutagenesis of Arg1018 to Ile. In the resultant R1018I mutant, the rate of thrombin activation and appearance of maximal cofactor activity was delayed and was consistent with delayed cleavage of the light chain at residue 1545. In contrast, the rate of factor Xa activation in the R1018I mutant was not altered. This finding suggests that thrombin cleavage at 1018 facilitates subsequent thrombin cleavage at 1545. Further mutagenesis was used to study the requirement for sequences within the factor V B- domain for thrombin cleavage at residue 1545. Whereas the factor V deletion molecule removing residues 709 to 1545 was not cleaved by thrombin, a smaller B-domain deletion molecule (residues 709 to 1476) containing an acidic amino acid-rich region (residues 1490 to 1520) was effectively cleaved by thrombin. These results show that residues 1476 to 1545, which contain an acidic amino acid-rich region, were required for thrombin cleavage of the light chain. Introduction of an acidic amino acid-rich region from factor VIII (residues 337 to 372) into the factor V 709 to 1545 deletion also restored thrombin cleavage of the light chain. In contrast, similar replacement with the acidic region from the factor VIII light chain (residues 1649 to 1689) was significantly less effective in promoting thrombin cleavage of the light chain. This finding suggests that the different acidic regions in factors V and VIII are not functionally equivalent in their interaction with thrombin.(ABSTRACT TRUNCATED AT 400 WORDS)     

Vasodilator agents and supracollicular transection fail to inhibit cortical spreading depression in the cat

It remains an open question as to whether cortical spreading depression (CSD) is the pathophysiological correlate of the neurological symptoms in migraine with aura. In the experimental animal, CSD is an electrophysiological phenomenon mainly mediated via NMDA receptors. However, according to case reports in humans, visual aura in migraine can be alleviated by vasodilator substances, such as amyl nitrite and isoprenaline. There is also circumstantial evidence that brainstem nuclei (dorsal raphe nucleus and locus coeruleus) may play a pivotal role in the initiation of aura. In this study, CSD was elicited in alpha-chloralose anesthetized cats by cortical needle stab injury and monitored by means of laser Doppler flowmetry. Topical application of isoprenaline (0.1-1%) and amyl nitrite (0.05%) onto the exposed cortex had no effect on the elicitation or propagation of CSD. Also, after supracollicular transection, subsequent CSDs showed no differences in the speed of propagation and associated flow changes. We conclude from these data that--given CSD probably exists in humans during migraine--spreading neurological deficits during migraine aura are independent of brainstem influence and have a primarily neuronal rather than vascular mechanism of generation.