Comparing the performance of 2 human papillomavirus assays for a new use indication: a real-world evidence-based evaluation in the United States

BACKGROUND

The US Food and Drug Administration supports innovations to facilitate new indications for high-risk human papillomavirus testing. This report describes the retrospective testing of stored specimens and analysis of existing data to efficiently and cost-effectively support a new indication for the Onclarity human papillomavirus assay (Becton, Dickinson and Company, BD Life Sciences - Integrated Diagnostic Solutions, Sparks, MD). The performance of this index test was compared with that of a predicate test, the cobas human papillomavirus assay (Roche Diagnostics, Indianapolis, IN). Both human papillomavirus assays are based on real-time polymerase chain reaction platforms that detect the presence of 14 high-risk human papillomavirus genotypes. The predicate assay reports human papillomavirus types 16 and 18 as individual results and the other 12 human papillomavirus genotypes as 1 pooled result. The index assay reports 9 independent results (human papillomavirus types 16, 18, 31, 33/58, 35/39/68, 45, 51, 52, and 56/59/66). Both the index and predicate assays are approved by the Food and Drug Administration for cervical cancer screening, but at the time that this study was initiated, the index human papillomavirus assay was not approved for use with cervical specimens collected in PreservCyt (Hologic, Inc, San Diego, CA) liquid-based cytology media.

OBJECTIVE

The performance of the index human papillomavirus assay was compared with that of the predicate human papillomavirus assay for the detection of cervical intraepithelial neoplasia grades 2 or greater and 3 or greater (≥CIN2 or ≥CIN3) using PreservCyt liquid-based cytology specimens collected from women aged 21 to 65 years. In addition, the ability of the index test's extended genotyping to stratify ≥CIN2 and ≥CIN3 risks, using these specimens, was evaluated.

STUDY DESIGN

The New Mexico HPV Pap Registry was used to select an age- and cytology-stratified random sample of 19,879 women undergoing opportunistic cervical screening and follow-up in routine clinical practice across New Mexico. A subset (n = 4820) of PreservCyt specimens was selected from 19,879 women for paired testing by the index and predicate human papillomavirus assays within age and cytology strata and included women with or without cervical biopsy follow-up. Point estimate differences and ratios were calculated for cervical disease detection and positivity rates, respectively, with 95% confidence intervals to determine statistical significance. The cumulative risk of ≥CIN2 or ≥CIN3, with up to 5-year follow-up, was estimated for the index assay using Kaplan-Meier methods.

RESULTS

The 5-year cumulative ≥CIN3 detection rates were 5.6% for the index assay and 4.6% for the predicate assay (difference, 1.0%; 95% confidence interval, 0.5%-1.5%). The ≥CIN3 positivity rates within <1 year were 95.3% for the index assay and 94.5% for the predicate assay (ratio, 1.01; 95% confidence interval, 0.98-1.06). The ≥CIN3 cumulative positivity rates for the index and predicate assays were also similar at 5 years. Among cases of ≥CIN3, the positive agreement rates between the index and predicate assays for human papillomavirus types 16 and 18 were 100.0% (95% confidence interval, 95.0%-100.0%) and 90.9% (95% confidence interval, 62.3%-98.4%), respectively. Human papillomavirus type 16 carried the highest ≥CIN2 or ≥CIN3 risk, followed by human papillomavirus types 18/31/33/58/52/45 and human papillomavirus types 35/56/59/51/56/59/66.

CONCLUSION

The index and predicate human papillomavirus assays demonstrated equivalent performance, and extended human papillomavirus genotyping, using the index assay, provided effective ≥CIN2 and ≥CIN3 risk stratification, supporting a new indication for use of the index assay with PreservCyt.

Research integrity in clinical trials: innocent errors and spin versus scientific misconduct

PURPOSE OF REVIEW

High-quality research underpins the best healthcare practice. This article focuses on analyzing the current literature to promote research integrity across clinical trials.

RECENT FINDINGS

Recent admissions of questionable practices by researchers have undermined practitioner and public confidence. There is limited evidence specifically for ethical and professional standards in clinical trials to guide researchers and institutions to embed integrity into research practice.

SUMMARY

Unintentional errors and spin in research are not uncommon as training in design and conduct of clinical trials is not part of health education for medical and allied health professions. There is unfamiliarity with procedures, such as prospective registration, a priori documentation of statistical analysis plans, openness in data sharing, and so forth. This, combined with the academic culture of secrecy, has led to an environment where scientific suspicion, instead of trust, is the norm. Existing science integrity documents are devoid of specific recommendations about how to translate any guidance into clinical trial practice. There is a need for constructive, supportive and multidisciplinary approaches based on open dialogue and continuous training, targeting the research environment. Research integrity now needs to take centre stage to re-instill confidence in randomized trial evidence to inform clinical practice.

Antigen-Based Testing but Not Real-Time Polymerase Chain Reaction Correlates With Severe Acute Respiratory Syndrome Coronavirus 2 Viral Culture

BACKGROUND

Individuals can test positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by molecular assays following the resolution of their clinical disease. Recent studies indicate that SARS-CoV-2 antigen-based tests are likely to be positive early in the disease course, when there is an increased likelihood of high levels of infectious virus.

METHODS

Upper respiratory specimens from 251 participants with coronavirus disease 2019 symptoms (≤7 days from symptom onset) were prospectively collected and tested with a lateral flow antigen test and a real-time polymerase chain reaction (rt-PCR) assay for detection of SARS-CoV-2. Specimens from a subset of the study specimens were utilized to determine the presence of infectious virus in the VeroE6TMPRSS2 cell culture model.

RESULTS

The antigen test demonstrated a higher positive predictive value (90%) than rt-PCR (70%) when compared to culture-positive results. The positive percentage agreement for detection of infectious virus for the antigen test was similar to rt-PCR when compared to culture results.

CONCLUSIONS

The correlation between SARS-CoV-2 antigen and SARS-CoV-2 culture positivity represents a significant advancement in determining the risk for potential transmissibility beyond that which can be achieved by detection of SARS-CoV-2 genomic RNA. SARS-CoV-2 antigen testing can facilitate low-cost, scalable, and rapid time-to-result, while providing good risk determination of those who are likely harboring infectious virus, compared to rt-PCR.

Factors that Influence the Reported Sensitivity of Rapid Antigen Testing for SARS-CoV-2

Tests that detect the presence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antigen in clinical specimens from the upper respiratory tract can provide a rapid means of coronavirus disease 2019 (COVID-19) diagnosis and help identify individuals who may be infectious and should isolate to prevent SARS-CoV-2 transmission. This systematic review assesses the diagnostic accuracy of SARS-CoV-2 antigen detection in COVID-19 symptomatic and asymptomatic individuals compared to quantitative reverse transcription polymerase chain reaction (RT-qPCR) and summarizes antigen test sensitivity using meta-regression. In total, 83 studies were included that compared SARS-CoV-2 rapid antigen-based lateral flow testing (RALFT) to RT-qPCR for SARS-CoV-2. Generally, the quality of the evaluated studies was inconsistent; nevertheless, the overall sensitivity for RALFT was determined to be 75.0% (95% confidence interval: 71.0-78.0). Additionally, RALFT sensitivity was found to be higher for symptomatic vs. asymptomatic individuals and was higher for a symptomatic population within 7 days from symptom onset compared to a population with extended days of symptoms. Viral load was found to be the most important factor for determining SARS-CoV-2 antigen test sensitivity. Other design factors, such as specimen storage and anatomical collection type, also affect the performance of RALFT. RALFT and RT-qPCR testing both achieve high sensitivity when compared to SARS-CoV-2 viral culture.

The Potential Clinical and Economic Value of a Human Papillomavirus Primary Screening Test That Additionally Identifies Genotypes 31, 45, 51, and 52 Individually

BACKGROUND

Although current human papillomavirus (HPV) genotype screening tests identify genotypes 16 and 18 and do not specifically identify other high-risk types, a new extended genotyping test identifies additional individual (31, 45, 51, and 52) and groups (33/58, 35/39/68, and 56/59/66) of high-risk genotypes.

METHODS

We developed a Markov model of the HPV disease course and evaluated the clinical and economic value of HPV primary screening with Onclarity (BD Diagnostics, Franklin Lakes, NJ) capable of extended genotyping in a cohort of women 30 years or older. Women with certain genotypes were later rescreened instead of undergoing immediate colposcopy and varied which genotypes were rescreened, disease progression rate, and test cost.

RESULTS

Assuming 100% compliance with screening, HPV primary screening using current tests resulted in 25,194 invasive procedures and 48 invasive cervical cancer (ICC) cases per 100,000 women. Screening with extended genotyping (100% compliance) and later rescreening women with certain genotypes averted 903 to 3163 invasive procedures and resulted in 0 to 3 more ICC cases compared with current HPV primary screening tests. Extended genotyping was cost-effective ($2298-$7236/quality-adjusted life year) when costing $75 and cost saving (median, $0.3-$1.0 million) when costing $43. When the probabilities of disease progression increased (2-4 times), extended genotyping was not cost-effective because it resulted in more ICC cases and accrued fewer quality-adjusted life years.

CONCLUSIONS

Our study identified the conditions under which extended genotyping was cost-effective and even cost saving compared with current tests. A key driver of cost-effectiveness is the risk of disease progression, which emphasizes the need to better understand such risks in different populations.

Human Papillomavirus Same Genotype Persistence and Risk: A Systematic Review

OBJECTIVE

The aim of the study was to examine whether high-grade cervical intraepithelial neoplasia (CIN) was more closely associated with human papillomavirus (HPV) same-genotype persistence (SGTP) versus clearance of prior infection with a subsequent infection by a new genotype (genotype switch [GS]), clearance of HPV infection, or acquisition of a new HPV infection after a negative infection status, during a follow-up testing subsequent to abnormal screening results.

MATERIALS AND METHODS

MEDLINE, Cochrane Library, Health Technology Assessment, and clinicaltrials.gov were searched from January 2000 to July 2019 for prospective controlled trials and observational studies of women and retrospective studies using HPV assays with extended- or full-genotype reporting. The primary outcome was high-grade CIN after at least 2 rounds of testing. Overall quality of evidence for the risk estimate outcomes was assessed. Of the 830 identified abstracts, 66 full-text articles were reviewed, and 7 studies were included in the synthesis. The study protocol was registered with the PROSPERO International Prospective Register of Systematic Reviews (CRD42018091093).

RESULTS

Continued HPV-positive women falls in 2 equally large groups: SGTP and GS. Sensitivity, positive predictive value, and positive likelihood ratio of SGTP were significantly higher than for GS. Human papillomavirus genotypes may be ranked into 3 tiers (immediate colposcopy, follow-up testing, return to routine screening), according to associated risk of persistence for high-grade CIN and to prevailing clinical action thresholds.

CONCLUSIONS

There is moderately high-quality evidence to support the clinical utility of SGTP to improve risk discrimination for high-grade CIN compared with qualitative HPV testing without genotype-specific information.

Clinical Evaluation of BD Veritor SARS-CoV-2 Point-of-Care Test Performance Compared to PCR-Based Testing and versus the Sofia 2 SARS Antigen Point-of-Care Test

The clinical performance of the BD Veritor System for Rapid Detection of SARS-CoV-2 nucleocapsid antigen (Veritor), a chromatographic immunoassay used for SARS-CoV-2 point-of-care testing, was evaluated using nasal specimens from individuals with COVID-19 symptoms. Two studies were completed to determine clinical performance. In the first study, nasal specimens and either nasopharyngeal or oropharyngeal specimens from 251 participants with COVID-19 symptoms (≤7 days from symptom onset [DSO], ≥18 years of age) were utilized to compare Veritor with the Lyra SARS-CoV-2 PCR assay (Lyra). In the second study, nasal specimens from 361 participants with COVID-19 symptoms (≤5 DSO, ≥18 years of age) were utilized to compare performance of Veritor to that of the Sofia 2 SARS Antigen FIA test (Sofia 2). The positive, negative, and overall percent agreement (PPA, NPA, and OPA, respectively) were the primary outcomes. In study 1, the PPA for Veritor, compared to Lyra, ranged from 81.8 to 87.5% across the 0 to 1 and 0 to 6 DSO ranges. In study 2, Veritor had PPA, NPA, and OPA values of 97.4, 98.1, and 98.1%, respectively, with Sofia 2. Discordant analysis showed one Lyra positive missed by Veritor and five Lyra positives missed by Sofia 2; one Veritor positive result was negative by Lyra. Veritor met FDA emergency use authorization (EUA) acceptance criteria for SARS-CoV-2 antigen testing for the 0 to 5 and 0 to 6 DSO ranges (PPA values of 83.9% and 82.4%, respectively). Veritor and Sofia 2 showed a high degree of agreement for SARS-CoV-2 detection. The Veritor test allows for more rapid COVID-19 testing utilizing easy-to-collect nasal swabs but demonstrated <100% PPA compared to PCR.

Nutritional and Dietary Interventions for Autism Spectrum Disorder: A Systematic Review

CONTEXT

Children with autism spectrum disorder (ASD) frequently use special diets or receive nutritional supplements to treat ASD symptoms.

OBJECTIVES

Our objective was to evaluate the effectiveness and safety of dietary interventions or nutritional supplements in ASD.

DATA SOURCES

Databases, including Medline and PsycINFO.

STUDY SELECTION

Two investigators independently screened studies against predetermined criteria.

DATA EXTRACTION

One investigator extracted data with review by a second investigator. Investigators independently assessed the risk of bias and strength of evidence (SOE) (ie, confidence in the estimate of effects).

RESULTS

Nineteen randomized controlled trials (RCTs), 4 with a low risk of bias, evaluated supplements or variations of the gluten/casein-free diet and other dietary approaches. Populations, interventions, and outcomes varied. Ω-3 supplementation did not affect challenging behaviors and was associated with minimal harms (low SOE). Two RCTs of different digestive enzymes reported mixed effects on symptom severity (insufficient SOE). Studies of other supplements (methyl B₁₂, levocarnitine) reported some improvements in symptom severity (insufficient SOE). Studies evaluating gluten/casein-free diets reported some parent-rated improvements in communication and challenging behaviors; however, data were inadequate to make conclusions about the body of evidence (insufficient SOE). Studies of gluten- or casein-containing challenge foods reported no effects on behavior or gastrointestinal symptoms with challenge foods (insufficient SOE); 1 RCT reported no effects of camel's milk on ASD severity (insufficient SOE). Harms were disparate.

LIMITATIONS

Studies were small and short-term, and there were few fully categorized populations or concomitant interventions.

CONCLUSIONS

There is little evidence to support the use of nutritional supplements or dietary therapies for children with ASD.

Agglutination of single catalyst particles during fluid catalytic cracking as observed by X-ray nanotomography

X-ray nanotomography of a complete FCC particle cluster reveals increased metal concentrations at the interface of agglutinated E-cat particles, which might play a crucial role E-cat particle clustering.

Metal accumulation at the catalyst particle surface plays a role in particle agglutination during fluid catalytic cracking.

Nitrous oxide for the management of labor pain: a systematic review

BACKGROUND

We systematically reviewed evidence addressing the effectiveness of nitrous oxide for the management of labor pain, the influence of nitrous oxide on women's satisfaction with their birth experience and labor pain management, and adverse effects associated with nitrous oxide for labor pain management.

METHODS

We searched the MEDLINE, EMBASE, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases for articles published in English. The study population included pregnant women in labor intending a vaginal birth, birth attendees or health care providers who may be exposed to nitrous oxide during labor, and the fetus/neonate.

RESULTS

We identified a total of 58 publications, representing 59 distinct study populations: 2 studies were of good quality, 11 fair, and 46 poor. Inhalation of nitrous oxide provided less effective pain relief than epidural analgesia, but the quality of studies was predominately poor. The heterogeneous outcomes used to assess women's satisfaction with their birth experience and labor pain management made synthesis of studies difficult. Most maternal adverse effects reported in the literature were unpleasant side effects that affect tolerability, such as nausea, vomiting, dizziness, and drowsiness. Apgar scores in newborns whose mothers used nitrous oxide were not significantly different from those of newborns whose mothers used other labor pain management methods or no analgesia. Evidence about occupational harms and exposure was limited.

CONCLUSIONS

The literature addressing nitrous oxide for the management of labor pain includes few studies of good or fair quality. Further research is needed across all of the areas examined: effectiveness, satisfaction, and adverse effects.

Progestogens for preterm birth prevention: a systematic review and meta-analysis by drug route

PURPOSE

Progestogen has been investigated as a preventive intervention among women with increased preterm birth risk. Our objective was to systematically review the effectiveness of intramuscular (IM), vaginal, and oral progestogens for preterm birth and neonatal death prevention.

METHODS

We included articles published from January 1966 to January 2013 and found 27 randomized trials with data for Bayesian meta-analysis.

RESULTS

Across all studies, only vaginal and oral routes were effective at reducing preterm births (IM risk ratio [RR] 0.95, 95 % Bayesian credible interval [BCI]: 0.88-1.03; vaginal RR 0.87, 95 % BCI: 0.80-0.94; oral RR 0.64, 95 % BCI: 0.49-0.85). However, when analyses were limited to only single births all routes were effective at reducing preterm birth (IM RR 0.77, 95 % BCI: 0.69-0.87; vaginal RR 0.80, 95 % BCI: 0.69-0.91; oral RR 0.66, 95 % BCI: 0.47-0.84). Only IM progestogen was effective at reducing neonatal deaths (IM RR 0.78, 95 % BCI: 0.56-0.99; vaginal RR 0.75, 95 % BCI: 0.45-1.09; oral RR 0.72, 95 % BCI: 0.09-1.74). Vaginal progestogen was effective in reducing neonatal deaths when limited to singletons births.

CONCLUSIONS

All progestogen routes reduce preterm births but not neonatal deaths. Future studies are needed that directly compare progestogen delivery routes.

Closing the quality gap: revisiting the state of the science (vol. 3: quality improvement interventions to address health disparities)

OBJECTIVE

This review evaluates the effectiveness of quality improvement (QI) strategies in reducing disparities in health and health care.

DATA SOURCES

We identified papers published in English between 1983 and 2011 from the MEDLINE® database, the Cumulative Index of Nursing and Allied Health Literature (CINAHL), Web of Science Social Science Index, and PsycINFO.

REVIEW METHODS

All abstracts and full-text articles were dually reviewed. Studies were eligible if they reported data on effectiveness of QI interventions on processes or health outcomes in the United States such that the impact on a health disparity could be measured. The review focused on the following clinical conditions: breast cancer, colorectal cancer, diabetes, heart failure, hypertension, coronary artery disease, asthma, major depressive disorder, cystic fibrosis, pneumonia, pregnancy, and end-stage renal disease. It assessed health disparities associated with race or ethnicity, socioeconomic status, insurance status, sexual orientation, health literacy/numeracy, and language barrier. We evaluated the risk of bias of individual studies and the overall strength of the body of evidence based on risk of bias, consistency, directness, and precision.

RESULTS

Nineteen papers, representing 14 primary research studies, met criteria for inclusion. All but one of the studies incorporated multiple components into their QI approach. Patient education was part of most interventions (12 of 14), although the specific approach differed substantially across the studies. Ten of the studies incorporated self-management; this would include, for example, teaching individuals with diabetes to check their blood sugar regularly. Most (8 of 14) included some sort of provider education, which may have focused on the clinical issue or on raising awareness about disparities affecting the target population. Studies evaluated the effect of these strategies on disparities in the prevention or treatment of breast or colorectal cancer, cardiovascular disease, depression, or diabetes. Overall, QI interventions were not shown to reduce disparities. Most studies have focused on racial or ethnic disparities, with some targeted interventions demonstrating greater effect in racial minorities--specifically, supporting individuals in tracking their blood pressure at home to reduce blood pressure and collaborative care to improve depression care. In one study, the effect of a language-concordant breast cancer screening intervention was helpful in promoting mammography in Spanish-speaking women. For some depression care outcomes, the collaborative care model was more effective in less-educated individuals than in those with more education and in women than in men.

CONCLUSIONS

The literature on QI interventions generally and their ability to improve health and health care is large. Whether those interventions are effective at reducing disparities remains unclear. This report should not be construed to assess the general effectiveness of QI in the health care setting; rather, QI has not been shown specifically to reduce known disparities in health care or health outcomes. In a few instances, some increased effect is seen in disadvantaged populations; these studies should be replicated and the interventions studied further as having potential to address disparities.

Middle cranial fossa transtemporal approach to the intrapetrous internal carotid artery

Diseases involving the proximity of the internal carotid artery at the skull base require identification of this vessel in the temporal bone to gain vascular control for any maneuver in its vicinity. This article details the technique of surgical dissection and exposure of the internal carotid artery within the skull base through a transtemporal middle cranial fossa approach. The anatomic landmarks important in utilizing this procedure include the greater superficial petrosal nerve, the mandibular branch of the trigeminal nerve, and the middle meningeal artery. With this approach, the internal carotid artery can be followed throughout the carotid canal and beyond the formen lacerun to the region of the cavernous sinus. The indications and limitations of this procedure are described and several clinical applications are provided.

Magnetic resonance imaging-guided fine needle aspiration for the diagnosis of skull base lesions

Magnetic resonance imaging (MRI)-guided fine needle aspiration was used to obtain tissue from lesions of the skull base for cytologic diagnoses in 14 patients. Our technique utilized a guiding system to enable three-dimensional orientation in a two-dimensional scan and a high nickel content 22 gauge needle to minimize significantly MRI artifact. Needle access to the skull base was provided through a subzygomatic or retromandibular approach. In seven of nine cases an accurate diagnosis was established by this technique and later confirmed by surgical exploration and histologic analysis. Failure to obtain a representative specimen from the lesion occurred in one case and difficulty in interpreting the cytologic features of the tissue was encountered in another case. The indications, limitations, and technical details of the procedure are described.

Inaccuracies introduced by single width blood pressure cuffs

Blood pressure cuff dimensions directly affect accuracy of blood pressure measurements. For accurate blood pressure measurements, the width of the cuff must be proportional to arm circumference. A cuff that is too narrow results in falsely high blood pressure values, and a cuff that is too wide results in falsely low values. Some blood pressure standards permit a single width cuff regardless of arm circumference. The purpose of this study was to evaluate whether 12 cm single width cuffs currently permitted by the British Hypertension Society (BHS) standard are sufficiently accurate to pass the Association for the Advancement of Medical Instrumentation (AAMI), BHS, and European Society of Hypertension (ESH) International Protocol (IP1) Working Group standards for accuracy. Each of 101 subjects was tested sequentially with both a single and a proportional width cuff in random order. Auscultatory blood pressure was determined by 2 observers using a double binaural stethoscope. Accuracy was determined by comparing the resulting differences with the AAMI, BHS, and IP1 standards for accuracy. The single width blood pressure cuff failed the AAMI accuracy standards for both systolic blood pressure on large arms and diastolic blood pressure on small and large arms, and overall. The single width cuffs, also, failed the BHS accuracy standards for diastolic BP. In conclusion, these single width cuffs could result in a significant number of people being misdiagnosed and mistreated for hypertension. Therefore, to avoid 'cuff hypertension' and 'cuff hypotension', the cuff width should be proportional to arm circumference.

Full-field transmission x-ray microscopy for bio-imaging

A full-field hard-x-ray microscope at SSRL has successfully imaged samples of biological and environmental origin at 40 nm resolution. Phase contrast imaging of trabeculae from a female mouse tibia, loaded in vivo to study the effects of weight-bearing on bone structure, revealed a complex network of osteocytes and canaliculi. Imaging of cordgrass roots exposed to mercury revealed nanoparticles with strong absorption contrast. 3D tomography of yeast cells grown in selenium rich media showed internal structure.

Renal amino acid, fat and glucose metabolism in type 1 diabetic and non-diabetic humans: effects of acute insulin withdrawal

AIMS/HYPOTHESIS

The aim of this study was to test the hypothesis that type 1 diabetes alters renal amino acid, glucose and fatty acid metabolism.

MATERIALS AND METHODS

We studied five C-peptide-negative, type 1 diabetic subjects during insulin replacement (glucose 5.6 mmol/l) and insulin deprivation (glucose 15.5 mmol/l) and compared them with six non-diabetic subjects. Leucine, phenylalanine, tyrosine, glucose and palmitate tracers were infused after an overnight fast and samples were obtained from the renal vein, femoral vein and femoral artery.

RESULTS

Insulin deprivation significantly increased whole-body fluxes (20-25%) of phenylalanine, tyrosine and leucine, and leucine oxidation (50%). Kidney contributed 5-10% to the whole-body leucine and phenylalanine flux. A net uptake of phenylalanine, conversion of phenylalanine to tyrosine (5 micromol/min) and net release of tyrosine (approximately 5 micromol/min) occurred across the kidney. Whole-body (three-fold) and leg (two-fold) leucine transamination increased but amino acid metabolism in the kidney did not alter with diabetes or insulin deprivation. Insulin deprivation doubled endogenous glucose production, renal glucose production was unaltered by insulin deprivation and diabetes (ranging between 100 and 140 micromol/min). Renal palmitate exchange was unaltered by insulin deprivation.

CONCLUSIONS/INTERPRETATION

In conclusion, kidney post-absorptively accounts for 5-10% of whole-body protein turnover, 15-20% of leucine transamination and 10-15% of endogenous glucose production, and actively converts phenylalanine to tyrosine. During insulin deprivation, leg becomes a major site for leucine transamination but insulin deprivation does not affect renal phenylalanine, leucine, palmitate or glucose metabolism. Despite its key metabolic role, insulin deprivation in type 1 diabetic patients does not alter many of these metabolic functions.

Preoperative detection of pancreatic insulinomas on multiphasic helical CT

OBJECTIVE

The objective was to analyze enhancement characteristics of insulinomas and to determine the ability of multiphase CT to localize these tumors.

MATERIALS AND METHODS

Prospective interpretations of multiphase helical CT scans were reviewed in 30 patients who had insulinomas resected over a 5-year period. CT scans were retrospectively reviewed to determine enhancement characteristics, tumor conspicuity in each phase of enhancement, and potential causes for false-negative findings.

RESULTS

Sixty-three percent (19/30) of tumors were identified on CT prospectively. An additional six tumors were visualized in retrospect, allowing characterization of 25 (83%) of 30 tumors. Most tumors were hyperdense on at least one phase (n = 19), three tumors were hypoattenuating, and three were isodense and pedunculated. Insulinomas were most conspicuous on the early phase in 15 patients and in the portal venous phase in three. All tumors that underwent pancreatic phase imaging were seen (13/13), whereas three of 18 arterial and six of 25 portal venous phase findings were inconclusive for tumor. In the six examinations with false-negative findings in which the tumor could be seen in retrospect, two tumors were isodense and pedunculated, three were in close proximity to vessels, and one had a cystic appearance.

CONCLUSION

Multiphasic CT has a moderate sensitivity in the detection of insulinomas. Most tumors are more conspicuous on the earlier phases of enhancement. The pancreatic phase may be more useful than the arterial phase. Potential sources of false-negative results include tumors adjacent to vessels, pedunculated morphology, or nonhyperattenuating lesions.

Non-insulinoma pancreatogenous hypoglycaemia syndrome

Background

The authors have reported a newly recognized hypoglyacemic disorder, non-insulinoma pancreatogenous hypoglycaemia syndrome (NIPHS), which is characterized by postprandial hyperinsulinaemic hypoglycaemia, negative 72-h fast, negative transabdominal and intraoperative ultrasonography, spiral computed tomography and coeliac axis angiography, positive selective arterial calcium stimulation test (SACST), absence of insulinoma but presence of islet hypertrophy and nesidioblastosis, and relief of symptoms from gradient-guided partial pancreatectomy. Experience with the next five patients with this disorder (6–10; 1998–1999) compared with the original five (1–5; 1996–1998) is reported.

Results

Wide age range, male predominance, postprandial occurrence of symptoms, negative radiological localization, nesidioblastosis/islet hypertrophy, but no insulinoma characterized all ten cases. Response to SACST indicated widespread islet hyperfunction in patients 1 and 5; limitation to distribution of the SPA and GDA in patients 3, 4, 6 and 8, to distribution of the SPA in patients 2, 7 and 9, and to distribution of the SMA in patient 10. Except for patient 5, pancreatic resection to the left of the SMV was performed when only the SPA was positive on the SACST. Patients 5 and 8 have had recurrence of symptoms; they resolved within 3 months for patient 5.

Conclusion

NIPHS can usually be treated successfully with gradient-guided partial pancreatectomy.

Percutaneous transhepatic endoluminal biliary biopsy with use of a 19-gauge gun

A technique was developed to perform endoluminal biliary biopsy with use of a commercially available 19-g gun. In 18 patients, a biopsy set consisting of an outer 7-F, 50-cm sheath, an inner curved 14-g metal cannula, and a 60-cm, 19-g biopsy gun with a 20-mm throw was employed to obtain tissue from suspicious-appearing biliary strictures via preexisting transhepatic tracts. The endoluminal biopsy was positive for neoplasm in 13 of 18 cases with three false negatives, one true negative, and one patient with insufficient follow-up. One biopsy was complicated by a hepatic artery pseudoaneurysm, which was successfully treated with coil embolization.

Diagnosis of endolymphatic hydrops in vivo with magnetic resonance imaging

HYPOTHESIS

High-resolution magnetic resonance imaging (MRI) at 1.5 T preferentially enhances the perilymph over endolymph after administration of contrast with gadodiamide, which allows for differentiation of the membranous labyrinth. Furthermore, this imaging allows for the detection of endolymphatic hydrops.

BACKGROUND

Endolymphatic hydrops is believed to be associated with a number of ear diseases, including Ménière's disease. Although the pathologic changes of overaccumulation of endolymph in the inner ear are obvious on postmortem histologic examination of the temporal bone, they have yet to be observed in a living organism. Previous attempts to visualize this condition with high-resolution contrast-enhanced computed tomographic imaging and MRI have been unsuccessful.

METHODS

Healthy pigmented guinea pigs underwent a unilateral surgical ablation of the endolymphatic sac to create endolymphatic hydrops in the ear. High-resolution temporal bone imaging was performed by use of a 1.5-T MRI system. Two-dimensional images were acquired by a spin-echo technique with and without contrast enhancement by gadodiamide.

RESULTS

T1-weighted gadodiamide contrast-enhanced MRI of the midmodiolar level of the cochlea demonstrated that the perilymph appeared to be preferentially enhanced relative to the endolymph, resulting in a clear distinction between the scalae of the inner ear. The contrast-enhanced T1-weighted MRI of the midmodiolar level of the hydropic cochlea demonstrated a significantly enlarged scala media in comparison with the normal cochlea in the same animal.

CONCLUSION

The demonstration of endolymphatic hydrops has been possible for the first time in vivo by the use of a standard 1.5-T MRI system. This research has important clinical implications: Specifically, this technique may allow for the noninvasive diagnosis of Ménière's disease.

Superior vena cava syndrome: relief with a modified saphenojugular bypass graft

Superior vena cava (SVC) syndrome is a disabling and potentially life-threatening complication. SVC revascularization can be achieved by means of endovascular or direct surgical reconstructions. In the patient on whom we report, these two options were not possible, and a peripheral venous bypass grafting procedure was done with a technical innovation. Right upper-extremity swelling developed in a 55-year-old woman after radiation therapy for lung carcinoma. A left subclavian vein Port-A-Cath induced extensive thrombosis of the left innominate, axillosubclavian, and jugular veins. She was referred to our institution with very symptomatic SVC syndrome after two failed endovascular interventions. The occlusion of both innominate veins and chronic thrombus extending into the left axillosubclavian and internal jugular veins was confirmed by means of a venogram. A third endovascular attempt failed. The presternal skin had severe radiation-induced damage precluding direct SVC reconstruction. A bypass grafting procedure from the right internal jugular to the femoral vein was performed with spliced bilateral greater saphenous veins tunneled inside an externally supported expanded polytetrafluoroethylene graft. Postoperatively, the patient had no symptoms, and graft patency was confirmed by means of duplex ultrasound scanning. A saphenojugular bypass grafting procedure can offer prompt and durable relief of SVC syndrome when endovascular or direct surgical reconstructions are not possible. This rarely used peripheral venous bypass grafting procedure was modified by tunneling the vein graft inside an externally supported polytetrafluoroethylene graft to prevent kinking or compression.

Balloon dilation compared to stenting of dominant strictures in primary sclerosing cholangitis

OBJECTIVE

In some patients with primary sclerosing cholangitis (PSC), a localized, high-grade (dominant) stricture may be the principal cause of symptoms and hyperbilirubinemia. The aim of this retrospective study was to compare the beneficial effects and risk of balloon dilation alone versus dilation followed by stenting in PSC patients with dominant strictures.

METHODS

Charts from a group of 1009 patients with PSC seen over 10 yr were reviewed to identify those patients who had undergone endoscopic or percutaneous therapeutic intervention. Procedural and clinical data were recorded.

RESULTS

A total of 71 PSC patients, median age of 49 yr (range 18-78 yr) were identified. Thirty-four patients were treated with endoscopic balloon dilation alone, and 37 patients were treated with balloon dilation plus stent placement. Stents were placed percutaneously (n = 19), endoscopically (n = 14), or using both interventions (n = 4). Both groups were comparable at baseline with regards to age, symptoms, and bilirubin level. The median duration of follow-up after intervention was similar in both groups. The number of intervention-related complications (30 vs 6, p = 0.001) as well as the incidence of acute cholangitis (p = 0.004) were more common in the stent group compared to the balloon dilation group. There were more complications related to percutaneous stent placement than endoscopic placement (23 vs 7. p = 0.001). There was no significant difference between the two groups with regards to improving cholestasis.

CONCLUSIONS

There was no additional obvious benefit from stenting after balloon dilation in the treatment of dominant strictures in PSC patients. Stenting was associated with more complications, and its role after dilation should be assessed in a randomized trial rather than being accepted as routinely indicated in this setting.

Polyarteritis nodosa: spectrum of angiographic findings

The purpose of this study was to review the positive angiographic findings in patients with polyarteritis nodosa (PAN). The authors reviewed the angiograms of 56 consecutive patients (25 women and 31 men; age range, 18-81 years; mean age, 55 years) with PAN and arterial abnormalities consistent with necrotizing vasculitis. Aneurysms were present in 27 patients and segments of ectasia were present in seven patients, for a total of 34 (61%) of 56 patients with aneurysmal lesions. The remaining 22 (39%) patients had arterial lesions that were occlusive: luminal irregularity, stenosis, or occlusion. All but one of the patients with an aneurysm also had occlusive lesions. Therefore, 55 (98%) of the 56 patients were found to have occlusive lesions. Skeletal muscle arteries were affected in 18 patients, nine in the extremities. The most frequent finding in patients with PAN was occlusive arterial lesions. Although the presence of aneurysms increases specificity for the diagnosis of PAN, many patients have only occlusive lesions. Involvement of skeletal muscle arteries was common.

Noninsulinoma pancreatogenous hypoglycemia syndrome: an update in 10 surgically treated patients

BACKGROUND

Neuroglycopenia from endogenous hyperinsulinism usually is caused by insulinomas in adults. We recently reported a novel hypoglycemic disorder in 5 patients (patients 1 to 5) with postprandial neuroglycopenia, negative 72-hour fasts, negative perioperative imaging studies, but positive calcium stimulation tests and islet hypertrophy and nesidioblastosis in the gradient-guided resected pancreata.

METHODS

In this report we compare our experience with 5 additional patients (patients 6 to 10) with this syndrome to that in the original report.

RESULTS

The clinical features of patients 6 to 10 were similar to those of patients 1 to 5. Each had positive calcium stimulation testing that guided the extent of the distal pancreatectomy and histologic evidence of islet cell hypertrophy or nesidioblastosis. All 10 patients are alive from 9 to 50 months after operation, 1 of whom had no amelioration of neuroglycopenia. Minor perioperative complications occurred in 3 patients. One patient has experienced repeated bouts of acute pancreatitis, pseudocyst formation, and exocrine insufficiency.

CONCLUSIONS

We have identified adult patients with severe, postprandial hyperinsulinemic hypoglycemia from diffuse islet cell disease, 80% of whom have been well palliated with surgery. The results in 7 men have been better than those in the 3 women for reasons that are not obvious.

Aortic fenestration for acute or chronic aortic dissection: an uncommon but effective procedure

BACKGROUND

Aortic fenestration is rarely required for patients with acute or chronic aortic dissection. To better define its role and the indications for its use and to evaluate its success at relieving organ or limb malperfusion, we reviewed our experience with direct fenestration of the aorta.

METHODS

A retrospective analysis of all consecutive aortic fenestrations performed between January 1, 1979, and December 31, 1999, was performed. Fourteen patients, 12 men and two women (mean age, 59.6 years; range, 43-81), underwent fenestration of the aorta. All patients were hypertensive and had a history of tobacco use. By Stanford classification, there were three type A and 11 type B patients. In the acute dissection group (n = 7), indications for surgery were malperfusion in six patients (leg ischemia, 4; renal ischemia, 5; bowel ischemia, 3) and intra-abdominal bleeding from rupture in two. In the chronic dissection group (n = 7), indications for surgery were abdominal aortic aneurysm in 4 patients (infrarenal, 3; pararenal, 1), thoracoabdominal aneurysm in 1, hypertension from coarctation of the thoracic aorta in 1, and aortic occlusion with disabling claudication in 1.

RESULTS

Emergency aortic fenestration was performed in seven patients (surgically for 6 and percutaneously for 1). Fenestration level was infrarenal in four and pararenal in three. Concomitant abdominal aortic graft replacement was performed in four patients, combined with ascending aortic replacement (n = 1) and bilateral aortorenal bypasses (n = 1). In two patients, acute fenestration was performed for organ malperfusion after prior proximal aortic replacement (ascending aorta, 1; descending thoracic aorta, 1). Seven elective aortic fenestrations were performed for chronic dissection (descending thoracic aorta, 2; paravisceral aorta, 2; infrarenal aorta, 2 and pararenal aorta, 1). Concomitant aortic replacement was performed in six patients (abdominal aorta, 5; thoracoabdominal aorta, 1). Fenestration was successful at restoring flow in all 10 patients with malperfusion. Operative mortality for emergency fenestration was 43% (3/7). The three deaths that occurred were of patients with anuria or bowel ischemia, or both. There were no postoperative deaths for elective fenestration. At a mean follow-up of 5.1 years, there were no recurrences of malperfusion and no false aneurysm formations at the fenestration site.

CONCLUSION

Fenestration of the aorta can effectively relieve organ or limb ischemia. Bowel ischemia and anuria are indicators of dismal prognosis and emergency fenestration in these patients carries a high mortality. Elective fenestration combined with aortic replacement can be performed safely in chronic dissection. Aortic fenestration is indicated for carefully selected patients with malperfusion and offers durable benefits.

Auditory threshold and inner ear pressure: measurements in experimental endolymphatic hydrops

HYPOTHESIS

Experimental endolymphatic hydrops leads to an endolymph-perilymph pressure imbalance that is responsible for the loss of auditory sensitivity in the ear.

BACKGROUND

This study investigates whether intralabyrinthine pressure is a factor in the auditory dysfunction of experimental endolymphatic hydrops.

METHODS

Auditory function was investigated in 10 guinea pigs 90 to 120 days after endolymphatic sac ablation by measuring compound action potentials in response to acoustic stimuli including alternating clicks and tone bursts of 0.5, 1, 2, 4, and 8 kHz. After auditory thresholds to the various stimuli were established, endolymphatic and perilymphatic pressures were measured with a no-flow micropressure measuring system. The cause of the hearing loss in Meniere's disease, especially in the early phases of this condition, remains an enigma. Histologic temporal bone preparations show a disproportion in the volume of endolymph to perilymph with an expanded and distorted membranous labyrinth. Speculation as to whether an endolymph-perilymph fluid pressure imbalance is responsible for these morphologic changes were raised by Hallpike and Cairns (1) in their initial report of the histopathology of Meniere's disease. Further speculation has questioned whether this pressure imbalance may be responsible for the symptoms and physical finding of this condition, including hearing loss. The ability to produce experimental endolymphatic hydrops in the guinea pig secondary to surgical occlusion of the endolymphatic sac and duct has been useful in studying various aspects of Meniere's disease (2). Investigators have been able to demonstrate auditory threshold shifts with hydrops. Elevated endolymph-perilymph pressure gradients have also been demonstrated (3). This

RESULTS

Increased auditory thresholds were noted in the hydrops ears at all tested parameters (p < 0.03). A relative increase in endolymph over perilymph pressure was found in hydrops ears as previously reported. The increase in endolymph-perilymph pressure of hydrops could not be correlated directly to the elevated auditory threshold shift.

CONCLUSION

Endolymphatic hydrops is a complex pathologic state with multiple inner ear alterations including abnormal intralabyrinthine pressure. Factors other than or in addition to pressure contribute to the auditory threshold shift of hydrops.

Gastric mucosal responses to intrahepatic portosystemic shunting in patients with cirrhosis

BACKGROUND & AIMS

The response of gastric mucosal lesions in cirrhotic patients with portal hypertension, namely, portal hypertensive gastropathy (PHG) and gastric vascular ectasia (GVE), to transjugular intrahepatic portosystemic shunts (TIPS) is not known.

METHODS

Clinical and laboratory evaluation, upper gastrointestinal endoscopy, and Doppler ultrasonography were performed before placement of TIPS and 6 weeks, 3 months, and 6 months after TIPS in 54 patients. Thirty patients had mild PHG, 10 had severe PHG, and 14 had GVE.

RESULTS

Approximately 75% of the patients with severe PHG responded to TIPS as shown by improvement in endoscopic findings and by a decrease in transfusion requirements; 89% of patients with mild PHG had endoscopic resolution. Patients with GVE had neither endoscopic resolution nor a decrease in transfusion requirements after TIPS. There was no difference in mortality between the 2 groups.

CONCLUSIONS

The results support the position that severe PHG and GVE may be different lesions. Mild and severe PHG respond to TIPS. Because GVE does not respond to TIPS, we recommend that TIPS be avoided for the treatment of gastrointestinal bleeding associated with GVE.

Hemosuccus pancreaticus complicating chronic pancreatitis: an obscure cause of upper gastrointestinal bleeding

BACKGROUND

Hemosuccus pancreaticus, a rare form of upper gastrointestinal bleeding, may complicate chronic pancreatitis and pose a significant diagnostic and therapeutic dilemma.

AIM

To present our experience with this potentially life-threatening complication of chronic pancreatitis.

METHODS

We reviewed our experience with management (both operative as well as angiographic embolization) of patients with hemosuccus pancreaticus complicating histologically documented chronic pancreatitis between 1976 and 1997. Diagnosis of hemosuccus pancreaticus was based on clinical presentation, preoperative endoscopic and radiographic imaging, operative findings, and pathologic evaluation.

RESULTS

During the period, we managed eight patients with hemosuccus pancreaticus (1.5% of all patients with chronic pancreatitis treated surgically). Gastrointestinal bleeding presented as hematemesis in three and hematochezia in three, but all had recent melena and were anemic; three of these patients were hemodynamically unstable. Abdominal pain was present in six. When performed, angiography (n=6) was diagnostic of a pseudoaneurysm; computed tomography (n=7) showed a pseudoaneurysm in two and a pseudocyst in five. Endoscopy (n=8) revealed blood issuing from the ampullary papilla in two patients. Operative management (n=6) involved distal pancreatectomy, pancreatoduodenectomy, or total pancreatectomy in two patients each. Angiographic embolization was successful in one patient, but the other died from uncontrollable hemorrhage.

CONCLUSIONS

Hemosuccus pancreaticus is rare, but should be considered in patients with chronic pancreatitis and gastrointestinal bleeding. In the absence of pancreatitis-related indications for surgery, angiographic embolization can be definitive treatment. If there are pancreatitis-related indications for operation, angiographic embolization may allow an elective operative procedure based on structural changes of the pancreas. If embolization fails, pancreatic resection is usually required, often on an emergent basis.

The roles of the pastor in the interdisciplinary rehabilitation team

People with chronic illnesses and functional limitations may face a lifetime of changes and adjustments. Often, the onset of a long-term illness or disease requires a person to rethink values and develop new coping strategies in order to adapt to a life-changing event. At such times, people may draw on sources of spiritual support, finding comfort from a pastor or other clergy. This article describes key roles taken by the clergy who provide these services. Patients discharged from inpatient rehabilitation units have reported using faith and prayer as effective coping strategies. Religious faith can have a positive influence on emotions and may be directly related to improved functional ability. Disciplines of faith, such as solitude, silence, and meditation, may promote mental health. Although this article presents information from a Christian church perspective, readers should note that services should be considered from a wide range of spiritual representatives.

Endovascular repair of abdominal aortic aneurysms: where do we stand?

Endovascular repair of abdominal aortic aneurysms has evolved dramatically within the past few years. In light of the potential to reduce morbidity and mortality associated with open surgical repair, endoluminal grafting offers therapeutic options to patients who are not surgical candidates because of comorbidities. With the development of bifurcated devices, more complex aneurysms may be treated by endovascular grafting. Although successful placement of endovascular grafts requires a pronounced learning curve, including appropriate patient selection, midterm results seem consistent with those of traditional open repair of aneurysms. This review describes the current indications, minimal requirements, different devices and associated techniques, and potential complications of endoluminal repair of abdominal aortic aneurysms. Future aspects of endoluminal grafting are also discussed.

Noninsulinoma pancreatogenous hypoglycemia: a novel syndrome of hyperinsulinemic hypoglycemia in adults independent of mutations in Kir6.2 and SUR1 genes

In adults, endogenous hyperinsulinemic hypoglycemia is almost invariably due to insulinoma. In these patients with insulinoma, neuroglycopenic episodes exclusively after meal ingestion and negative 72-h fasts are extraordinarily rare. We describe five adults with neuroglycopenic episodes from hyperinsulinemic hypoglycemia within 4 h of meal ingestion and negative 72-h fasts. Each had negative transabdominal ultrasonography, spiral computed tomographic scanning, and celiac axis angiography of the pancreas. However, all showed positive selective arterial calcium stimulation tests indicative of pancreatic beta-cell hyperfunction. At pancreatic exploration, no insulinoma was detected by intraoperative ultrasonography and complete mobilization and palpation of the pancreas. Moreover, the resected pancreata showed islet hypertrophy and nesidioblastosis, but no insulinoma. No definite disease-causing mutation was detected in Kir6.2 and SUR1 genes, which encode the subunits of the pancreatic ATP-sensitive potassium channel responsible for glucose-induced insulin secretion. Four patients who underwent gradient-guided partial pancreatectomy have been free of hypoglycemic symptoms for up to 3 yr follow-up; the other, who underwent a limited distal pancreatectomy, has had brief recurrence of symptoms. The unique clinical features and responses to dynamic testing in these adults with hyperinsulinemic hypoglycemia in the absence of insulinoma may constitute a new syndrome of postprandial hypoglycemia from diffuse beta-cell hyperfunction.

Preoperative hepatic artery chemoembolization followed by orthotopic liver transplantation for hepatocellular carcinoma

In our experience, the primary obstacle precluding the widespread use of orthotopic liver transplantation (OLT) for definitive therapy of hepatocellular carcinoma (HCC), even for early-stage disease, is preventing tumor recurrence. Chemoembolization is an attractive strategy to minimize tumor progression before OLT because of its shown antitumor effect, ability to be repeated, and minimal systemic toxicity. Thus, this pilot study was undertaken to determine the tolerability and treatment outcomes of pretransplantation chemoembolization of HCC followed by OLT. Between 1992 and 1997, 27 patients with HCC who had cirrhosis, no extrahepatic metastasis, less than three tumor nodules of less than 5 cm each, and no evidence of vascular invasion on preoperative imaging studies were enrolled onto the protocol. Chemoembolization was performed using Ivalon particles with mitomycin, doxorubicin, and cisplatin. Twenty-four patients completed the protocol with chemoembolization and a liver transplant. The mean United Network of Organ Sharing waiting time was 167 days. Chemoembolization was well tolerated. On examination of the explanted liver, the majority of patients had a single lesion, mean tumor size was 3.66 cm (range, 1.5 to 6 cm), and the majority of patients had stage II disease. None of the transplant recipients has developed recurrent HCC (mean follow-up, 29.2 months; range, 9 to 55 months). The 1- and 2-year disease-free survival rates are 91% and 84%, respectively. In conclusion, chemoembolization followed by OLT is well tolerated and associated with excellent outcomes in selected patients with HCC.

Determinants of plasma fibrin D-dimer sensitivity for acute pulmonary embolism as defined by pulmonary angiography

BACKGROUND

The reported operating characteristics of the plasma fibrin D-dimer level for the diagnosis of acute pulmonary embolism vary widely.

OBJECTIVE

To determine the sensitivity, specificity, predictive value, and clinical utility of the D-dimer for the diagnosis of pulmonary embolism, and to describe the effect of D-dimer assay method (enzyme-linked immunosorbent assay [ELISA], latex agglutination, membrane ELISA) and discriminate level, patient location at onset, comorbid disease, duration and intensity of concurrent heparin administration, and duration of symptoms on these operating characteristics.

DESIGN

Prospective laboratory investigation.

SETTING

Community and tertiary care teaching hospital.

PATIENTS

Consecutive patients with suspected acute pulmonary embolism referred for pulmonary angiography from April 1993 through March 1996.

MEASUREMENTS

Baseline characteristics, the duration and intensity of heparin anticoagulation, the time interval between symptom onset and plasma D-dimer testing, pulmonary angiography, and the D-dimer level on the day of pulmonary angiography.

RESULTS

Of 105 consenting patients, 33 (31%) had a positive pulmonary angiogram. The D-dimer sensitivity/ negative predictive value for the ELISA, latex agglutination (American Bioproducts Co/Diagnostica Stago and Biopool International), and membrane ELISA were 100%/100%, 94%/94%, 100%/100%, and 97%/96%, respectively, at a discriminate level of 250 microg/L or less. The clinical utility, defined as the prevalence of a negative test, ranged from 17% to 33%. D-dimer sensitivity was unaffected by patient location at onset, comorbid disease, or heparin therapy but was inversely related to the duration of symptoms.

CONCLUSIONS

The sensitivity of the plasma fibrin D-dimer for the diagnosis of pulmonary embolism depends on the assay method, the assay-specific discriminate level, and the duration of symptoms. At the appropriate discriminate level, the plasma D-dimer is a sensitive but nonspecific test for the diagnosis of pulmonary embolism.

Laboratory experience with experimental endolymphatic hydrops

Experimental endolymphatic hydrops refers to the creation of hydrops in the experimental animal and represents a histologic correlate for Meniere's disease. Details of the surgical means to create this condition in guinea pigs are provided. Alterations in endolymph fluid composition and relative endolymph pressure occur with hydrops. Deterioration in auditory and vestibular function secondary to hydrops can develop.

Vestibular and optokinetic function in the normal guinea pig

Vestibular and optokinetic function was quantitatively studied in the normal guinea pig through investigation of the vestibulo-ocular reflex (VOR), optokinetic nystagmus (OKN), and the visual vestibulo-ocular reflex (VVOR) by means of sinusoidal stimulation with a computer-controlled rate table (VOR and VVOR) or an optokinetic drum. The VOR exhibited high-pass filter characteristics with steady state gain achieved at 0.125 Hz. The maximum gain was 0.55 at a velocity of 60 degrees/s. The VOR was modeled by a transfer function with best fits obtained with an adaptation time constant of 12.5 seconds. The OKN showed low-pass filter characteristics with a decrease in gain for increase in stimulus amplitude. The maximum gain measured was 0.64. A fractional pole model provided a fit of these data. The VVOR exhibited a mean gain of between 0.6 and 0.7 across the stimulus bandwidth and peak velocities. A model based on a linear combination of the actual OKN and VOR gains provided an estimate of the VVOR gain.

The dissected aorta: percutaneous treatment of ischemic complications--principles and results

PURPOSE

Describe the principles and results of percutaneous treatment of ischemic complications of aortic dissection.

MATERIALS AND METHODS

Twenty-four patients with aortic dissection complicated by ischemic compromise of the liver or bowel (n = 15), kidney (n = 18), or lower extremity (n = 13) were evaluated by means of aortography, intravascular ultrasound, and manometry, and were treated percutaneously. Visceral arteries were classified as obstructed or nonobstructed. Obstruction was classified as static, in which the dissecting hematoma extended into and narrowed the lumen of a branch artery, or dynamic, in which the dissection flap prolapsed into the vessel origin or narrowed the true lumen (TL) above it. Treatment consisted of vascular stents alone (n = 4), or balloon fenestration (n = 20) without (n = 8) or with (n = 12) vascular stents.

RESULTS

Obstruction was present in 77 arteries and was static in 12 arteries, dynamic in 45 arteries, static and dynamic in 17 arteries, and indeterminate in three arteries. Percutaneous treatment did not alter false lumen (FL) pressure, but reduced the peak systolic interluminal pressure gradient from 28 mm Hg to 2 mm Hg and restored flow in 71 of 77 arteries (92%). Six patients died within 30 days (25% operative mortality), none as a result of the procedure. Two additional patients died in follow-up from complications of an expanding FL. Technical complications in two patients due to altered hemodynamics after initial intervention were recognized and corrected percutaneously during the same procedure.

CONCLUSIONS

Percutaneous fenestration and endovascular stent deployment are indicated to restore blood flow to arteries compromised by aortic dissection. The prognosis of patients is related to the ischemic injury sustained prior to the percutaneous interventional procedure and, in patients with acute type I dissection who have not undergone surgery, to the preoperative stability of the FL.

The dissected aorta: part III. Anatomy and radiologic diagnosis of branch-vessel compromise

PURPOSE

To determine the anatomic, hemodynamic, and radiologic characteristics of branch-vessel compromise in patients with aortic dissection.

MATERIALS AND METHODS

Sixty-two patients with aortic dissection were evaluated with aortography (n = 62), intravascular ultrasound (US) (n = 35), and manometry (n = 56). Branch-vessel compromise with ischemia was suspected in 40 of these patients. Radiologic and manometric findings were correlated with clinical findings of ischemia. Femoral artery pulse strength was correlated with access from the respective femoral artery to the true and false lumina of the dissected aorta.

RESULTS

Twenty-six of 40 patients suspected of having ischemia had angiographic evidence of branch-vessel compromise, and intravascular US helped identify two types of branch-vessel compromise in them: static (dissection intersected and narrowed the vessel origin) and dynamic (dissection spared the vessel origin, but the dissection flap appeared to compress the true lumen at or above the origin and covered the origin). False-lumen pressure in classic dissections exceeded (n = 16) or equaled (n = 30) true-lumen pressure. Branch vessels that arose exclusively from the false lumen were well perfused. Findings of a dissection flap oriented concave toward the false lumen were 91% sensitive and 72% specific for a true-lumen pressure deficit.

CONCLUSION

Intravascular US and manometric findings clarify the mechanisms of branch-vessel compromise after aortic dissection and provide a rational guide for percutaneous treatment.

Long-term results of hepatic artery fluorodeoxyuridine and conformal radiation therapy for primary hepatobiliary cancers

PURPOSE

We have previously shown that conformal radiation therapy (RT) combined with hepatic artery (HA) fluorodeoxyuridine (FdUrd) had encouraging hepatic control and survival rates for patients with nondiffuse primary hepatobiliary malignancies. With longer follow-up, we were particularly interested if long-term hepatic control and disease-free survival could be achieved, and if late hepatic complications due to radiation therapy were observed.

METHODS AND MATERIALS

Patients with unresectable primary hepatobiliary cancer were treated with concurrent HA FdUrd (0.2 mg/kg/day) and conformal RT (1.5-1.65 Gy per fraction, twice a day), directed only to the liver abnormalities. Three-dimensional treatment planning was used to define both the target and normal liver volumes. The total dose of radiation (48 or 66 Gy) was determined by the fractional volume of normal liver excluded from the high dose volume. Patients were followed routinely for response, patterns of failure, long-term toxicity, and survival. The median potential follow-up was 54 months.

RESULTS

A total of 22 patients (11 with hepatocellular carcinoma and 11 with cholangiocarcinoma) were treated. There were 10 objective responses in the 11 evaluable patients. The overall freedom from hepatic progression at more than 2 years was about 50%. The median survival was 16 months with an actuarial 4-year survival of about 20%. Gastrointestinal bleeding was the most common long-term toxicity. Late hepatic toxicity was not observed; in fact, hypertrophy of the untreated liver was seen.

CONCLUSIONS

Combined conformal RT and HA FdUrd can produce long-term freedom from hepatic progression and survival in patients with unresectable, nondiffuse primary hepatobiliary malignancies. There were no long-term liver complications observed.

Oxidation states of the manganese cluster during the flash-induced S-state cycle of the photosynthetic oxygen-evolving complex

The Mn K-edge x-ray absorption spectra for the pure S states of the tetranuclear Mn cluster of the oxygen-evolving complex of photosystem II during flash-induced S-state cycling have been determined. The relative S-state populations in samples given 0, 1, 2, 3, 4, or 5 flashes were determined from fitting the flash-induced electron paramagnetic resonance (EPR) multiline signal oscillation pattern to the Kok model. The edge spectra of samples given 0, 1, 2, or 3 flashes were combined with EPR information to calculate the pure S-state edge spectra. The edge positions (defined as the zero-crossing of the second derivatives) are 6550.1, 6551.7, 6553.5, and 6553.8 eV for S0, S1, S2, and S3, respectively. In addition to the shift in edge position, the S0--> S1 and S1--> S2 transitions are accompanied by characteristic changes in the shape of the edge, both indicative of Mn oxidation. The edge position shifts very little (0.3 eV) for the S2--> S3 transition, and the edge shape shows only subtle changes. We conclude that probably no direct Mn oxidation is involved in this transition. The proposed Mn oxidation state assignments are as follows: S0 (II, III, IV, IV) or (III, III, III, IV), S1 (III, III, IV, IV), S2 (III, IV, IV, IV), S3 (III, IV, IV, IV).