Head-up tilt test in complicated neurocardiogenic syncope in children.

To confirm the usefulness of head-up tilt test (HUT) in neurocardiogenic syncope (NCS) with complicating clinical features, retrospective analysis were done on 12 selected children. The age at onset was 12.7 +/- 1.9 (mean +/- SD) years. Associated clinical features were postoperative congenital heart disease (PO CHD) in 3, coexistent arrhythmia in 8 (persistent ventricular arrhythmia during exercise in 3, premature ventricular contractions in 2, ventricular couplets in 1, sinoatrial exit block in 1 and resting sinus bradycardia in 1) and ST segment depression during exercise in 1. Four of them had a history of exercise-related syncope. All 3 patients with PO CHD had arrhythmia (ventricular tachycardia in 1, sinus bradycardia in 1 and atrioventricular block in 1). HUT provoked NCS in 8 (2 during baseline tilt, 6 during isoproterenol infusion). In one each, ventricular tachycardia and loss of consciousness without hypotension and bradycardia were induced. Atenolol was tried in 5 with improvement of NCS in 4 and aggravation of dizziness in 1. During follow-up, 7 became asymptomatic (2 with atenolol) and 5 were stationary. In conclusion, HUT was valuable in diagnosing NCS even in children with complicating clinical features such as arrhythmias or PO CHD. HUT could be done as apart of initial diagnostic tests if the past history suggests NCS, regardless of associated clinical features. In some cases, the unexpected results of the test turned out useful in managing children with syncope or dizziness.     

The effect of beta adrenergic stimulation on QT and QTc interval in syncope children with or without coexisting ventricular arrhythmias

We investigated the effect of beta-adrenergic stimulation on the heart rate and QT interval in syncope children with or without coexisting ventricular arrhythmias (VA). Of the 24 children who presented with syncope or presyncope and showed negative tilt test, 13 were classified into a group with VA and the remaining 11 without VA. The provocative test was performed in bolus infusion and continuous infusion. RR, QT, and QTc intervals on routine 12-lead surface electrocardiogram were obtained during each stage of isoproterenol infusion. In all cases, malignant ventricular arrhythmia and syncope were not induced by isoproterenol provocative test. RR and QT intervals were shortened and QTc intervals were prolonged as the isoproterenol dose was increased in both groups and methods. The QTc interval reached its peak level after the bolus injection of 1.0 microgram and during the continuous infusion of 0.03 microgram/kg/min. The two groups showed no significant difference in the QTc interval change according to the infusion methods. This study indicates that changes in the heart rate and QT interval by beta-adrenergic stimulation were not different according to the coexisting ventricular arrhythmias in syncope children with negative head-up tilt test.     

The diagnostic sensitivity of electrophysiologic testing in patients with syncope caused by transient bradycardia

Although electrophysiologic testing accurately delineates abnormalities in patients with fixed cardiac-conduction defects, its sensitivity in identifying transient rhythm disturbances is unknown. We prospectively studied 21 patients who had electrocardiographically documented intermittent atrioventricular block (n = 13) or sinus pauses (n = 8) causing syncope, but whose cardiac rhythm had reverted to normal by the time of referral. There were 14 men and 7 women, with a mean age (+/- SD) of 63 +/- 13 years. Fourteen patients had organic heart disease, and 8 were taking cardioactive medications. Electrophysiologic testing was performed before the implantation of a permanent pacemaker. Only three of the eight patients with documented sinus pauses had abnormalities during their tests that suggested the correct diagnosis (sensitivity, 37.5 percent), including a prolonged sinus-node recovery time in one and carotid-sinus hypersensitivity in two. Three of the eight patients had abnormalities detected that were unrelated to syncope, including atrial flutter, dual atrioventricular nodal pathways, and sustained monomorphic ventricular tachycardia. Of the 13 patients with documented atrioventricular block, only 2 had abnormalities suggesting the correct diagnosis (sensitivity, 15.4 percent). Additional observations unrelated to syncope among these 13 patients included abnormal sinus-node function, atrial flutter, and atrial fibrillation causing hypotension. These preliminary observations suggest that a negative electrophysiologic test in a patient with a normal cardiac rhythm who has experienced syncope does not exclude a transient bradyarrhythmia as a cause of the syncope. Furthermore, electrophysiologic testing may sometimes reveal unrelated rhythm disturbances that may mistakenly be designated as the cause of the syncope.     

Sympathetic nerve activity in hypotension and orthostatic intolerance

AIM: The present paper reviews how changes in sympathetic nerve activity are related to hypotensive episodes and orthostatic intolerance in humans. RESULTS: It has been well documented that sympathetic neural traffic to skeletal muscles (muscle sympathetic nerve activity; MSNA) plays an essential role in maintaining blood pressure homeostasis mainly through baroreflex. The MSNA responded to gravitational loading from the head to the leg (+Gz) during passive head-up tilt (HUT). Patients who suffered from orthostatic hypotension with or without syncope were classified into at least two groups; low and high responders of MSNA to orthostatic loading. The typical examples belonging to the former group were patients of multiple system atrophy who had very low basal sympathetic outflow to muscle which responded extremely poorly to HUT. Patients of multiple system atrophy presented also postprandial hypotension in which muscle sympathetic response to oral glucose administration was absent. The latter group was represented by subjects who manifested vasovagal syncope with normal or even higher muscle sympathetic response to HUT, which was suddenly withdrawn concomitantly with bradycardia and hypotension. Similar withdrawal of sympathetic nerve traffic to muscle was encountered in a rare case of idiopathic non-orthostatic episodic hypotension which accompanied bradycardia. The MSNA was suppressed by short-term exposure to microgravity but was enhanced after long-term exposure to microgravity. Orthostatic intolerance after long-term exposure to microgravity was related to progressive reduction of muscle sympathetic response to orthostatic loading with impaired arterial baroreflex. CONCLUSION: It is concluded that hypotensive episodes are closely related to poor or lack of muscle sympathetic outflow, but may depend on various neural mechanisms to induce it.     

Decreased entropy of symbolic heart rate dynamics during daily activity as a predictor of positive head-up tilt test in patients with alleged neurocardiogenic syncope

Entropy measures of RR interval variability during daily activity over a 24h period were compared in 30 patients with a positive head-up tilt (HUT) test and 30 patients with a negative HUT test who had a history of alleged neurocardiogenic syncope. Two different entropies, approximate entropy (ApEn) and entropy of symbolic dynamics (SymEn), were employed. In patients showing a positive HUT test, the entropies were significantly decreased when compared with the patients with a negative HUT test. In addition, SymEn in the patients with a negative HUT test was significantly lower than in the normal controls. Discriminant analysis using SymEn could correctly identify 89.3% (520/582) of the 1 h RR interval data of the patients with a positive HUT test regardless of the time of day. Baseline entropies of heart rate dynamics during daily activity were found to be significantly lower in patients with alleged neurocardiogenic syncope and a positive HUT test than in those with the same history but with a negative HUT test. The decreased entropy of symbolic heart rate dynamics may be of predictive value of a positive HUT test in patients with alleged neurocardiogenic syncope.     

Arg389Gly β1-adrenergic receptor polymorphism and susceptibility to syncope during tilt test

Introduction

Numerous hormones, neurotransmitters, and other stimuli exert their biological effect on cellular functioning through heptahelical receptors coupled to G proteins (GPCR – G protein-coupled receptors). Adrenergic receptors that belong to this superfamily of receptors are components of the sympathetic nervous system. They play a pivotal role in blood pressure regulation and myocardial contractility. Alterations of the adrenergic receptor pathway have been suggested to be involved in the pathophysiology of vasovagal syncope (VVS). The aim of the present study was to evaluate the distribution of Arg389Gly polymorphism within the ADRB1 gene among patients with recurrent syncope.

Material and methods

Arg389Gly single nucleotide polymorphism was analyzed in 205 patients with recurrent syncope. Ninety-five patients (46%) had a positive head-up tilt test (HUT) result. The control group comprised 143 non-fainting subjects. Genotyping was performed by restriction fragment length polymorphism (RFLP) with BstNI enzyme.

Results

Both analyzed groups had similar distribution of the 389Gly allele. Sixty percent of polymorphic 389Gly carriers belong to the group of syncopal patients, while 40% belong to the control group of healthy subjects.

Conclusions

An association between syncopal incidence and Arg389Gly polymorphism within the ADRB1 gene was not found. The analyzed polymorphism affecting sympathetic activity does not influence vasovagal syncope in Polish patients.     

Cardiovascular response during head-up tilt in chronic fatigue syndrome.

This study examined the cardiovascular response to orthostatic challenge, and incidence and mechanisms of neurally mediated hypotension in chronic fatigue syndrome (CFS) during a head-up tilt test. Stoke volume was obtained by a thoracic impedance cardiograph, and continuous heart rate and blood pressure were recorded during a 45-min 70 degrees head-up tilt test. Thirty-nine CFS patients and 31 healthy physically inactive control subjects were studied. A positive tilt, i.e. a drop in systolic blood pressure of > 25 mmHg, no concurrent increase in heart rate and/or development of presyncopal symptoms, was seen in 11 CFS patients and 12 control subjects (P > 0.05). During baseline and the first 5 min of head-up tilt, CFS patients had higher heart rate and smaller pulsatile-systolic area than control subjects (P < 0.05). Among subjects who completed the test, those with CFS had higher heart rate and smaller stroke volume (P < 0.05) than corresponding control subjects. When comparing those who had a positive test outcome in each group, CFS patients had higher heart rates and lower pulse pressure and pulsatile-systolic areas during the last 4 min before being returned to supine (P < 0.05). These data show that there are baseline differences in the cardiovascular profiles of CFS patients when compared with control subjects and that this profile is maintained during head-up tilt. However, the frequency of positive tilts and the haemodynamic adjustments made to this orthostatic challenge are not different between groups.     

免疫性血栓症和习惯性流产的标志物—抗血管五糖（VPS）抗体的检测

目的：探讨血栓形成和习惯性流产发病的免疫机理。方法：利用ELISA法测定人血清中的抗－VPS抗体,结果：96例血栓症中,18例抗－VPS抗体阳性（18．8％）,34例习惯性流产有16例阳性（47．1％）,164例无血栓形成史的自身免疫性疾病及其它疾病仅3例阳性（1．8％）正常人61例均阴性（0％）,阳性病例抗－VPS抗体OD值明显高于正常人,18例阳性血栓症中的8例和16例阳性习惯性流产中的14例抗磷脂抗体（aPL)检测阴性。实验室发现,抗磷脂抗体（aPL）阴性而抗－VPS抗体阳性的病例组显示与APTT延长或血小板减少无关,然而,在抗磷脂抗体（aPL)阳性组病例则通常与此相关,结论：抗VPS抗体参与血栓形成和习惯性流产发病过程,可作为此类疾病的标志物而用于临床观察。     

Familial neurocardiogenic (vasovagal) syncope

Vasovagal syncope (VSS) is an exaggerated tendency towards the common faint caused by a sudden and profound hypotension with or without bradycardia. The etiology of VVS is unknown though several lines of evidence indicate central and peripheral abnormalities of sympathetic function. Studies however indicate a strong heritable component to the etiology of VVS in over 20% of cases. Here, we report the findings from a family that shows apparently autosomal dominant VVS in at least three generations. Clinical findings included an absence of any discernible cardiac or autonomic abnormalities and reproducible hypotension on tilt table testing in affected family members.     

Syncope in children and adolescents living in north-eastern Poland – scope of causes

PurposeTo investigate the diagnostic yield of different tests and asses the scope of causes in children referring to the hospital with a syncope in north-eastern Poland.MethodsA review of 386 consecutive patients (age 2–18 years) living in north-eastern Poland presenting to the cardiology department with a new onset syncope (which appeared to be neurally mediated by history) was undertaken. The patients underwent physical examination, laboratory tests, electrocardiography, 24-holter monitoring, head-up tilt-test, exercise test, echocardiography and electroencephalography. All the tests were performed in most of the patients, without ending the diagnostics after finding the first probable cause of loss of consciousness.Results229 potential causes of syncope were found in 191 patients (49.4%), with 2 possible causes in 32 patients and 3 potential causes in 3 patients. The top 3 tests with the highest diagnostic yield were: head-up tilt test (41.4%), 24-holter monitoring (14.5%) and echocardiography (8.4%). Electroencephalography was useful in 3 patients (1.5%) and exercise test did not help in any patient.ConclusionIn some children more than one potential cause of syncope was diagnosed. That might confirm multiple factors’ causality of syncope. Head-up tilt-test has the highest diagnostic yield in children with syncope. If the diagnostic protocol is not very strict, one might find some crucial conditions in about 8.3% of patients.     

Abnormal beta adrenergic responsiveness in allergic subjects: analysis of isoproterenol-induced cardiovascular and plasma cyclic adenosine monophosphate responses

Beta adrenergic responses were compared between normal control subjects and patients with allergic asthma or allergic rhinitis and a group of asymptomatic individuals with positive immediate hypersensitivity skin tests. Two responses to infused isoproterenol were monitored: increases in pulse pressure and plasma cyclic adenosine monophosphate (cyclic AMP). Although the normal control subjects responded with increases in pulse pressure of greater magnitude than the other groups in response to infused isoproterenol, the differences in responsiveness were more apparent when the concentration of isoproterenol required to increase the pulse pressure ≧22 mm Hg was compared. The 25 control subjects required 8.04 ± 0.48 ng/kg/min isoproterenol, whereas the 17 asthmatic patients required 14.25 ± 1.21 (p < 0.0001), the eight subjects with allergic rhinitis required 12.75 ± 1.58 (p < 0.0005), and the seven asymptomatic subjects with positive skin tests needed 11.1 ± 1.26 (p < 0.01). Comparison of baseline plasma cyclic AMP levels of the groups revealed no apparent differences. However, the normal controls responded to isoproterenol with larger increases in plasma cyclic AMP than the other groups at both 6 and 9 ng/kg/min. Furthermore, significantly fewer of the subjects with asthma, rhinitis, or positive skin tests demonstrated an increase in plasma cyclic AMP ≧ 50% above baseline as compared with controls. Thus, as reflected in both cardiovascular and cyclic AMP responses to infused isoproterenol, allergic asthmatic subjects are hyporesponsive as compared with normal controls. However, a comparable degree of diminished responsiveness is seen in subjects with allergic rhinitis or in asymptomatic individuals with positive skin tests. Therefore beta adrenergic hyporesponsiveness appears to be related with the atopic state rather than with asthma.     

Delaying orthostatic syncope with mental challenge: a pilot study

At orthostatic vasovagal syncope there appears to be a sudden decline of sympathetic activity. As mental challenge activates the sympathetic system, we hypothesized that doing mental arithmetic in volunteers driven to the end point of their cardiovascular stability may delay the onset of orthostatic syncope. We investigated this in healthy male subjects. Each subject underwent a head up tilt (HUT)+ graded lower body negative pressure (LBNP) up to presyncope session (control) to determine the orthostatic tolerance time, OTT (Time from HUT commencement to development of presyncopal symptoms/signs). Once the tolerance time was known, a randomized crossover protocol was used: either 1) Repeat HUT+LBNP to ensure reproducibility of repeated run or 2) HUT+LBNP run but with added mental challenge (2 min before the expected presyncope time). Test protocols were separated by 2 weeks. Our studies on five male test subjects indicate that mental challenge improves orthostatic tolerance significantly. Additional mental loading could be a useful countermeasure to alleviate the orthostatic responses of persons, particularly in those with histories of dizziness on standing up, or to alleviate hypotension that frequently occurs during hemodialysis or on return to earth from the spaceflight environment of microgravity.     

动态心电图与直立倾斜试验对不明原因晕厥的诊断价值探讨

目的探讨动态心电图(DCG)与直立倾斜试验(TTT)对不明原因晕厥的诊断价值。方法所有患者均常规进行查体、DCG、心脏超声、脑血流图、脑电图等检查,排除癫痫、短暂脑缺血发作(TIA)等疾患,考虑为血管迷走性晕厥(VVS)者,则进行TTT试验。(1)动态心电图检查:每例患者记录24h,监测导联为CM1,CM3和CM5,应用回放式计算机分析系统,分析和判断患者的心律失常与晕厥的关系,(2)直立倾斜试验检查:让患者倾斜站立于60°～90°的倾斜板上15min,每分钟测血压,并连续心电监护,观察血压、心率的变化。如诱发出晕厥或类似平时晕厥发作症状则停止试验。对未诱发出症状者,则让患者再平卧5～10min进行倾斜加异丙肾上腺素试验。结果294例不明原因晕厥患者中,经DCG检出心源性晕厥91例(31.0%),TTT检出VVS149例(50.6%),仍不能查明晕厥原因54例(18.4%)。结论DCG是诊断心律失常引起的心源性晕厥最有效的手段之一,阴性时也不能排除心源性晕厥;DCG对未发作VVS者几乎无价值,而TTT对VVS的诊断却具有重要的临床价值。     

Prevalence and impact factors of recurrent positive SARS-CoV-2 detection in 599 hospitalized COVID-19 patients

ObjectivesRepeat-positive tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in individuals with coronavirus disease 2019 (COVID-19) were common. We aimed to investigate the rate and risk factors of recurrent positive detection of SARS-CoV-2 in hospitalized individuals with COVID-19.MethodsOropharyngeal and nasopharyngeal swabs (n = 3513) were collected to detect SARS-CoV-2 during the hospitalization. We analysed the recurrent positive rate after consecutive negative results and its relationship to demographic characteristics.ResultsAmong 599 enrolled individuals with COVID-19, the median time for viral RNA shedding was 24 days (interquartile range 19–33 days). The positive rates of RT-PCR were 35.9% (215/599), 17.0% (65/383) and 12.4% (23/185) after one, two and three consecutive negative RT-PCR test results, respectively. Medians of Ct values of initial positive test, rebound positive test after two consecutive negative results, and rebound positive after three consecutive negative results were 28.8, 32.8 and 36.1, respectively. Compared with male patients, females had a significantly higher rate of recurrent positive RT-PCR after three consecutive negative results (18.2%, 18/99, versus 5.8%, 5/86; p 0.013). Older individuals (≥55 years) had a significantly higher rate of recurrent positive RT-PCR after one negative result (42.3%, 165/390, versus 23.9%, 50/209; p < 0.001). Nasopharyngeal swab tests produced a higher positive rate than oropharyngeal swab tests (37.3%, 152/408, versus 35.8%, 1111/3105).ConclusionOur study revealed the prevalence and dynamic characteristics of recurrent positive RT-PCR to SARS-CoV-2. We showed that around 17.0% (65/383) of patients tested positive for SARS-CoV-2 after two consecutive negative results. Patients with a rebound positive RT-PCR test had a low viral load. Older age and being female were risk factors for recurrent positive results.     

Basophil responsiveness in patients with insect sting allergies and negative venom-specific immunoglobulin E and skin prick test results

Background Current guidelines do not adequately address the question of how best to manage patients with a convincing history of insect allergy, but negative venom-specific IgE and skin test results.
Methods Forty-seven patients out of a total of 1219 (4%), with a positive history of sting allergy, were recruited over a period of 4.5 years. All recruited patients had a convincing history of a severe or a life-threatening anaphylactic reaction of Mueller grade II–IV (median grade III) after Hymenoptera sting, but negative venom-specific IgE and skin prick test results. Diagnostic work-up was prospectively followed by the CD63 basophil activation test and by intradermal skin testing. A control group of 25 subjects was also assessed.
Results Thirty-five out of 47 (75%) patients demonstrated a positive basophil CD63 response after stimulation with bee and/or wasp venom. Intradermal venom skin tests were performed for 37 patients, 17 (46%) of whom showed positive results. Out of 20 patients who demonstrated negative intradermal test results, 12 patients showed a positive CD63 response (60%). In contrast, out of 9 patients who showed a negative CD63 response, only one was detected by intradermal testing (11%). In the control group, only two out of 25 (4%) subjects displayed a positive basophil response and/or intradermal test.
Conclusion Here we show that, in complex cases with inconclusive diagnostic results, the CD63 activation test could be particularly useful and more sensitive than intradermal skin testing.     

Comparison of in vivo and in vitro tests in the diagnosis of imported fire ant sting allergy

The specificities and sensitivities of skin test reactivity to imported fire ant (IFA) whole body extract (WBE) and IFA venom were compared with IFA WBE RAST and IFA venom RAST in the diagnosis of IFA allergy. Study groups consisted of 18 IFA allergic patients and 21 control subjects with no history of allergy to insect stings. All IFA allergic patients had positive skin tests to both IFA WBE and IFA venom. Six of 21 (29%) control subjects also had positive skin tests to both IFA WBE and IFA venom. A commercial IFA WBE RAST was positive in 10 of 18 (56%) IFA-allergic patients and 2 of 21 (10%) control subjects. Imported fire ant aqueous venom RAST was positive in 11 of 11 (100%) IFA-allergic patients and three of ten (30%) control subjects. Vespa IFA venom RAST was positive in 16 of 18 (89%) IFA-allergic patients and 5 of 21 (24%) controls. The sensitivities and specificities of IFA WBE skin testing, IFA venom skin testing, and IFA venom RAST did not differ significantly. Imported fire ant WBE RAST was less sensitive than the other diagnostic methods.     

Screening for carriers of Tay-Sachs disease among Ashkenazi Jews. A comparison of DNA-based and enzyme-based tests

BACKGROUND AND METHODS. The prevention of Tay-Sachs disease (GM2 gangliosidosis, type 1) depends on the identification of carriers of the gene for this autosomal recessive disorder. We compared the enzyme-based test widely used in screening for Tay-Sachs disease with a test based on analysis of DNA. We developed methods to detect the three mutations in the HEXA gene that occur with high frequency among Ashkenazi Jews: two mutations cause infantile Tay-Sachs disease, and the third causes the adult-onset form of the disease. DNA segments containing these mutation sites were amplified with the polymerase chain reaction and analyzed for the presence of the mutations. RESULTS. Among 62 Ashkenazi obligate carriers of Tay-Sachs disease, the three specific mutations accounted for all but one of the mutant alleles (98 percent). In 216 Ashkenazi carriers identified by the enzyme test, DNA analysis showed that 177 (82 percent) had one of the identified mutations. Of the 177, 79 percent had the exon 11 insertion mutation, 18 percent had the intron 12 splice-junction mutation, and 3 percent had the less severe exon 7 mutation associated with adult-onset disease. The results of the enzyme tests in the 39 subjects (18 percent) who were defined as carriers but in whom DNA analysis did not identify a mutant allele were probably false positive (although there remains some possibility of unidentified mutations). In addition, of 152 persons defined as noncarriers by the enzyme-based test, 1 was identified as a carrier by DNA analysis (i.e., a false negative enzyme-test result). CONCLUSIONS. The increased specificity and predictive value of the DNA-based test make it a useful adjunct to the diagnostic tests currently used to screen for carriers of Tay-Sachs disease. Although some false positive results may be desirable on an enzyme-based test that is used in screening, the DNA test allows precise definition of the carrier state for the known mutations.     

Present and future of cardiac function tests: electrophysiologic tests]

Various electrocardiographic and physiologic tests have been developing for almost 100 years since Einthoven established the standard 12 lead electrocardiogram(ECG) system. Recently, interest has focused on the new developing parameters associated with cardiac ventricular repolarization, such as transmural dispersion of repolarization, T wave alternans and QT dispersion. QT dispersion, measured as interlead difference of QT interval, has been suggested to reflect regional variation of ventricular repolarization. However, still unsolved basic problems give difficulties for clinical acceptance of this parameter. On the other hand, it is generally accepted that heart rate variability obtained from Holter ECG is useful tool to assess the autonomic tone. Head-up tilt test is a valuable diagnostic tool to identify patients with neurally mediated syncope and also useful for assessment of reflex cardiac autonomic function, such as baroreflex sensitivity. The number of electrophysiologic study(EPS) dramatically increased together with increase of radiofrequency catheter ablation. A new three-dimensional nonfluoroscopic electroanatomical mapping system(CARTO) is an exciting development in catheter ablation treatment. Transtelephonic ECG and its computer-assisted answering system are also useful for diagnose and treatment in the patients of paroxysmal cardiac symptoms.     

Provocation-challenge studies in shrimp-sensitive individuals

Thirty individuals with history of immediate, objective, adverse reactions after shrimp ingestion underwent double-blind, placebo-controlled shrimp-food challenges. All individuals who did not exhibit a positive response (reproduction of objective symptoms) were administered an open challenge of 16 whole cooked shrimp. Positive challenge responses occurred in 9/30 subjects (30%); six of these subjects experienced a positive response during the double-blind phase. Of the 21 remaining subjects, 12 experienced generalized pruritus as their only symptom, whereas nine subjects had completely negative challenge responses. All placebo challenges were negative. Although a positive skin test was strongly associated with challenge symptoms (p less than 0.001), the shrimp prick skin test titration end points were not different among the challenge groups. The serum shrimp RAST percent was significantly higher in the positive challenge group (p less than 0.02). Mean levels of shrimp-specific serum IgG, IgA, and IgM levels were not different among the challenge groups. Although no single immunologic variable could be consistently used to identify subjects more likely to exhibit a positive challenge response, the composite of a positive shrimp prick skin test and elevated serum shrimp-specific IgE (RAST percent label bound greater than 11%) demonstrated a correct predictive value of 87% in this group of shrimp-sensitive subjects.     

Evaluation of penicillin hypersensitivity: Value of clinical history and skin testing with penicilloyl-polylysine and penicillin G : A cooperative prospective study of the penicillin study group of the American Academy of Allergy

A multicenter cooperative study of almost 3,000 patients by members of the Penicillin Study Group of the American Academy of Allergy has confirmed the usefulness of skin tests to penicillin G (Pen G) and penicilloyl-polylysine (PPL) in the evaluation of penicillin hypersensitivity. Nineteen percent of 1,718 patients with a history of penicillin allergy had positive skin tests to either or both agents, vs 7% of 1,229 patients with no such history. Among patients with a history of penicillin allergy where a detailed history was available, positive skin tests were noted in 46% with a history of anaphylaxis, 17% with a history of urticaria or angioneurotic edema, and 7% with a history of a maculopapular reaction. PPL Generally gave somewhat higher reaction rates than Pen G, but both skin tests were needed to elicit the maximum number of reactors. After skin tests were completed, 379 patients were challenged with penicillin. Six percent of patients with a positive history had an allergic reaction vs 2% of patients with a negative history. However, 67% of the 9 challenged patients with a positive skin test had an allergic reaction, and half of these were immediate or early systemic reactions. Only 3% of the 346 challenged patients with a negative skin test had a reaction to challenge and only one fourth of these had early reactions thought to be possibly mediated by IgE.