Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “IRT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1999

Blood concentrations of pancreatitis associated protein in neonates: relevance to neonatal screening for cystic fibrosis.

AIM: To determine whether pancreatitis associated protein (PAP) is a marker for cystic fibrosis which could be used in neonatal screening for the disease. METHODS: PAP was assayed on screening cards from 202,807 neonates. Babies with PAP > or = 15 ng/ml, or > or = 11.5 ng/ml and immunoreactive trypsinogen (IRT) > or = 700 ng/ml were recalled for clinical examination, sweat testing, and cystic fibrosis transmembrane regulator (CFTR) gene analysis. RESULTS: Median PAP value was 2.8 ng/ml. Forty four cases of cystic fibrosis were recorded. Recalled neonates (n = 398) included only 11 carriers. A receiver operating characteristic curve analysis showed that PAP above 8.0 ng/ml would select 0.76% of babies, including all those with cystic fibrosis, except for one with meconium ileus and two with mild CFTR mutations. Screening 27,146 babies with both PAP and IRT showed that only 0.12% had PAP > 8.0 ng/ml and IRT > 700 ng/ml, including all cases of cystic fibrosis. CONCLUSION: PAP is increased in most neonates with cystic fibrosis and could be used for CF screening. Its combination with IRT looks promising.

Acute-Phase Proteins↗
PubMed1983

beta Cell reserve in cystic fibrosis patients and heterozygotes.

An assessment of beta cell and exocrine pancreatic reserve based on fasting C peptide and immunoreactive trypsin (IRT) concentrations was carried out in non-diabetic (fasting blood glucose less than 6 mmol/l) patients with cystic fibrosis (CF; n = 20) and their parents (heterozygotes; n = 26). These indices were also measured in comparable control subjects (n = 20) and insulin-dependent diabetics (IDDs). C peptide concentrations in 18 CF patients were markedly lower than those in controls, and in 18 were comparable to those in IDDs (n = 27). Fasting C peptide concentration in heterozygotes was also significantly lower than that in controls and was significantly greater than that in IDDs. IRT concentrations in CF patients and heterozygotes were also significantly lower than those in controls. The frequency of subnormal C peptide concentrations was greater in CF patients with non-measurable IRT than in those who had residual IRT in their sera. These data show for the first time that the diminution in beta cell reserve in CF patients may be of a magnitude similar to that in IDDs in spite of their normal blood glucose and HbA1 concentrations. Therefore, these patients may have enhanced insulin sensitivity. CF heterozygotes too have a significant diminution in endocrine and exocrine pancreatic reserve when compared with the controls.

Adolescent↗
PubMed1980

Trypsin radioimmunoassay in the diagnosis of chronic pancreatitis.

Serum immunoreactive trypsin (IRT) determination has been recommended as a screening test in chronic pancreatitis. Using a commercial radioimmunoassay kit (RIA--gnost Trypsin; Behring-Werke, Marburg/Lahn, FRG) the interassay coefficient of variation was 26--44% for three different test sera. Gel filtration chromatography profiles revealed immunoreactivity in the position of 125I-trypsin and (less than 50%) in the void volume. The test was evaluated in controls (n = 90), chronic relapsing pancreatitis (CRP;n = 60) and after total pancreatectomy (n = 5). In 65% of the CRP cases decreased IRT values were found, whereas during acute attacks of CRP supranormal and normal values were found. After total pancreatectomy IRT levels were undetectable. It is concluded that the sensitivity of this IRT test is limited and that the available test system needs improvement.

Cholecystokinin↗
PubMed1987

Molecular size distribution of immunoreactive trypsin and renal tubular dysfunction: role in trypsin plasma-urine transfer.

In order to investigate the role of circulating free trypsinogen and renal tubular dysfunction in affecting trypsin plasma-urine transfer, serum immunoreactive trypsin (IRT), its urinary output, IRT molecular size distribution, filtrable immunoreactive trypsin, gamma-glutamyltransferase and alpha-glucosidase outputs were studied in 6 control subjects, 9 patients with pancreatic cancer and 15 with chronic pancreatitis. The majority of immunoreactivity was always eluted at a molecular weight of about 24,000 and might therefore be considered as free trypsinogen. Variable amounts of IRT at higher molecular weights, possibly represented by trypsin-inhibitor complexes, were also detected. Increasing IRT levels were generally accounted for by free trypsinogen, regardless of the nature of the disease. Unlike serum free trypsinogen levels, renal tubular damage, evaluated by means of the excretion of two high-molecular weight urinary enzymes, seems to play a prominent role in explaining trypsin plasma-urine transfer.

Adolescent↗
PubMed2003

Repeat intracoronary radiation for recurrent in-stent restenosis in patients who failed intracoronary radiation.

BACKGROUND: Intracoronary radiation therapy (IRT) is the only proven treatment for in-stent restenosis (ISR). It is, however, associated with a significant failure rate. The present study evaluated the outcomes of patients who underwent repeat intracoronary radiation for recurrent ISR. METHODS AND RESULTS: Fifty-one consecutive patients who failed a previous radiation treatment, presented with angina and angiographic evidence of ISR, and were treated with percutaneous coronary intervention (PCI) and repeat radiation to the same segment were studied. Twenty-five patients were treated with gamma radiation in a dose of 15 Gy, and 26 were treated with beta radiation doses of 18.3 to 23 Gy. The mean cumulative dose for this cohort was 39.5+/-11.9 Gy (range, 29 to 75.6 Gy). The outcomes of those patients were compared with outcomes of 299 patients who also failed initial radiation but were treated with repeat conventional PCI to a previously irradiated segment without repeat radiation. At 9 months after treatment, the repeat-IRT group had lower rates of target lesion revascularization (23.5% versus 54.6%; P<0.001) and major adverse cardiac events, including target vessel revascularization (29.4% versus 61.3%; P<0.001). At 9 months, patients with repeat IRT were free of angiographic and clinical events related to the radiation therapy. CONCLUSIONS: Repeat gamma or beta radiation to treat failed IRT for ISR after conventional PCI is safe and effective at 9 months and should be considered as a therapeutic option for this difficult patient subset.

Angina Pectoris↗
PubMed1985

Evidence for pancreas injury in adult respiratory distress syndrome.

The purpose of this study was to investigate the relation between serum lipase (LP), serum immunoreactive trypsin (IRT), and its inhibitors in patients with adult respiratory distress syndrome (ARDS) of diverse origin and to compare their time course with other acute conditions. The IRT and LP levels were determined at regular intervals in 41 patients hospitalized in the intensive respiratory unit with ARDS (n = 9), acute pancreatitis (n = 5), shock (n = 9), bronchopneumonia (n = 10), or acute cardiogenic pulmonary edema (n = 8). Several trypsin inhibitors were measured simultaneously: serum trypsin inhibitory capacity (TIC), alpha 1-antitrypsin, alpha 2-macroglobulin, and antithrombin III. Concomitantly, angiotensin-converting enzyme (ACE) activity was determined as a potential marker of the endothelial injury. A respective 19- and 13-fold increase in IRT and LP values were observed in patients with ARDS after a mean evolution of 6 days; similar increases were seen in patients with pancreatitis. These values were significantly higher than those observed in the other conditions studied. In patients with ARDS and acute pancreatitis, the evolution of IRT and LP values were associated with a sixfold rise in TIC. A low TIC/IRT ratio in patients with ARDS appeared to be an index of poor prognosis. Conversely, ACE activity evolution was characterized by an early decrease in all the conditions studied. These observations indicate that there is an acute delayed pancreas injury in ARDS. Thus, the release of pancreatic enzymes are not reliable markers of the early evolution of the disease but they may represent secondary mediators for enhancement of the increased endothelial permeability.

Adult↗
PubMed2000

Item response theory in personality assessment: a demonstration using the MMPI-2 depression scale.

Item response theory (IRT) analyses have, over the past 3 decades, added much to our understanding of the relationships among and characteristics of test items, as revealed in examinees response patterns. Assessment instruments used outside the educational context have only infrequently been analyzed using IRT, however. This study demonstrates the relevance of IRT to personality data through analyses of Scale 2 (the Depression Scale) on the revised Minnesota Multiphasic Personality Inventory (MMPI-2). A rich set of hypotheses regarding the items on this scale, including contrasts among the Harris-Lingoes and Wiener-Harmon subscales and differences in the items measurement characteristics for men and women, are investigated through the IRT analyses.

Adult↗
PubMed1984

Determination and characterization of immunoreactive trypsin in amniotic fluid from normal and cystic fibrosis fetuses.

High concentrations of immunoreactive trypsin (IRT) in the blood, and low concentrations of trypsin activity in fecal specimens have been found in newborn infants with cystic fibrosis (CF). The amniotic fluid concentrations of IRT and of IRT in complex with alpha 1-antitrypsin (alpha 1AT) were studied in 39 samples taken in about the 17th gestational week, and in 7 samples taken because the mothers had previously given birth to children with CF. The midtrimester samples contained trypsin in complex with alpha 1AT in a concentration of 30-200 micrograms/liter, and small amounts of trypsinogen, 0-50 micrograms/liter. Three of four amniotic fluid samples from CF fetuses had very low concentrations of trypsin in complex with alpha 1AT (less than 10 micrograms/liter), and only small amounts of trypsinogen (less than 10 micrograms/liter). Further prospective studies are needed to ascertain whether the determination of IRT in amniotic fluid may be of use in prenatal diagnosis of CF.

Amniocentesis↗
PubMed2003

A discussion of modern versus traditional psychometrics as applied to personality assessment scales.

Item response theory (IRT) methods are used by large testing firms, state agencies, and school districts to construct, analyze, and score most major aptitude, achievement, proficiency, entrance, and professional licensure exams. Personality assessment, in contrast, has not generally adopted these more powerful, modern psychometric techniques. We evaluate the possible role of IRT in the personality domain by highlighting key areas in which IRT and traditional methods differ. Although we conclude that IRT has a significant role to play in future personality measurement, there are many systemic and technical barriers to its routine application.

Forecasting↗
PubMed2005

Item response theory and the measurement of clinical change.

An instrument's sensitivity to detect individual-level change is an important consideration for both psychometric and clinical researchers. In this article, we develop a cognitive problems measure and evaluate its sensitivity to detect change from an item response theory (IRT) perspective. After illustrating assumption checking and model fit assessment, we detail 4 features of IRT modeling: (a) the scale information curve and its relation to the bandwidth of measurement precision, (b) the scale response curve and how it is used to link the latent trait metric with the raw score metric, (c) content-based versus norm-based score referencing, and (d) the level of measurement of the latent trait scale. We conclude that IRT offers an informative, alternative framework for understanding an instrument's psychometric properties and recommend that IRT analyses be considered prior to investigations of change, growth, or the effectiveness of clinical interventions.

Adult↗
PubMed2003

Impact of imagery rehearsal treatment on distressing dreams, psychological distress, and sleep parameters in nightmare patients.

We investigated the impact of imagery rehearsal treatment (IRT) on nightmare frequency, psychological distress, and sleep quality using polysomnography (PSG). 12 chronic nightmare patients completed prospective dream logs, measures of psychological distress, and underwent PSG prior to and 8.5 weeks following a single IRT session. Post-treatment, significant reductions were observed in retrospective nightmare frequency (d = 1.06, p = .007), prospective bad dream frequency (d = 0.53, p = .03), and anxiety scores (d = 1.01, p = .004). Minimal sleep alterations were found post-IRT, and varied as a function of nightmare etiology. The results independently replicate the efficacy of IRT for alleviating disturbing dreams and psychological distress. Sleep improvement may occur later in the recovery process.

Adult↗
PubMed2000

Systemic hypertension and impaired glucose tolerance are independently correlated to the severity of the acromegalic cardiomyopathy.

Increased mortality from cardiovascular diseases has been reported in acromegaly. Our objective was to evaluate the impact of glucose tolerance abnormalities and/or systemic hypertension in further worsening the acromegalic cardiomyopathy. The study design was open transversal. The subjects studied were 130 consecutive naive acromegalic patients (74 women and 56 men; age, 17-80 yr). Interventricular septum (IST) and left ventricular (LV) posterior wall thickness (PWT), LV mass index (LVMi), maximal early to late diastolic flow velocity ratio (E/A), isovolumic relaxation time (IRT), and LV ejection fraction (EF) were measured by echocardiography. The results were analyzed in line with the presence of glucose tolerance abnormalities (normal in 60, impaired in 38, diabetes mellitus in 32) and the presence (in 46) or absence (in 84) of hypertension. Patients with impaired glucose tolerance and diabetes mellitus had significantly higher age (P = 0.01), and systolic (P = 0.01) and diastolic (P = 0.01) blood pressures and lower E/A (P = 0.01) and EF (P = 0.01) than those with normal glucose tolerance. Disease duration, circulating GH and insulin-like growth factor I (IGF-I) levels, IST, LVPWT, LVMi, and IRT were similar in the 3 groups. Normotensive patients had significantly lower age (P<0.001), LVPWT (P<0.001), IST (P = 0.003), LVMi (P<0.001), and IRT (P = 0.02) and significantly higher E/A (P<0.001) and EF (P<0.001) than hypertensive subjects. Disease duration, circulating GH, and IGF-I levels were similar in the 2 groups. Multiple regression analysis showed that systolic blood pressure was the strongest predictor of LVMi (P = 0.0004), followed by GH levels (P = 0.02), whereas diastolic blood pressure was the strongest predictor of LVEF reduction (P<0.0001), followed by glucose tolerance status (P = 0.02). Age was the strongest predictor of both E/A impairment (P<0.0001) and IRT (P = 0.01), followed by IGF-I levels (P = 0.02). Compared to patients with uncomplicated acromegaly, those with hypertension but without abnormalities of glucose tolerance had an increased prevalence of LV hypertrophy (75% vs. 37.2%) as well as of impaired diastolic (50% vs. 7.8%) and systolic function (18.7% vs. 3.9%), whereas patients with glucose tolerance abnormalities but without hypertension had only an increased prevalence of impaired diastolic (39.7%) and systolic function (31.7%). The subgroup of acromegalic patients suffering from hypertension and diabetes mellitus had the highest prevalence of LV hypertrophy (84.6%), diastolic filling abnormalities (69.2%), and impaired systolic function at rest (53.9%). A careful cardiac investigation should thus be performed in all acromegalic patients showing these complications.

Acromegaly↗
PubMed2006

Response inhibition during Differential Reinforcement of Low Rates (DRL) schedules may be sensitive to low-level polychlorinated biphenyl, methylmercury, and lead exposure in children.

BACKGROUND: Animal studies have shown that exposure to common, low-level environmental contaminants [e.g., polychlorinated biphenyls (PCBs), lead] causes excessive and inappropriate responding on intermittent reinforcement schedules. The Differential Reinforcement of Low Rates task (DRL) has been shown to be especially sensitive to low-level PCB exposure in monkeys. OBJECTIVES: We investigated the relationships between prenatal PCB and postnatal Pb exposure performance on a DRL schedule in children. We predicted that a) prenatal PCB exposure would reduce interresponse times (IRTs) and reinforcements earned, and b) postnatal Pb exposure would reduce IRTs and reinforcements earned. METHODS: We tested 167 children on a DRL20 (20 sec) reinforcement schedule, and recorded IRTs and the number of reinforced responses across the session. We measured prenatal PCB exposure (cord blood), methylmercury (MeHg) (maternal hair), and postnatal Pb exposure (venous blood), and > 50 potentially confounding variables. RESULTS: Results indicated impaired performance in children exposed to PCBs, MeHg, and Pb. Children prenatally exposed to PCBs responded excessively, with significantly lower IRTs and fewer reinforcers earned across the session. In addition, exposure to either MeHg or Pb predicted statistically significant impairments of a similar magnitude to those for PCBs, and the associated impairments of all three contaminants (PCB, MeHg, and Pb) were statistically independent of one another. CONCLUSIONS: These results, taken with animal literature, argue the high sensitivity of DRL performance to low-level PCB, MeHg, and Pb exposure. Future research should employ behavioral tasks in children, such as DRL, that have been demonstrably sensitive to low-level PCB, MeHg, and Pb exposure in animals.

Analysis of Variance↗
PubMed2002

Non-linear dynamics of operant behavior: a new approach via the extended return map.

Previous efforts to apply non-linear dynamic tools to the analysis of operant behavior revealed some promise for this kind of approach, but also some doubts, since the complexity of animal behavior seemed to be beyond the analyzing ability of the available tools. We here outline a series of studies based on a novel approach. We modified the so-called 'return map' and developed a new method, the 'extended return map' (ERM) to extract information from the highly irregular time series data, the inter-response time (IRT) generated by Skinner-box experiments. We applied the ERM to operant lever pressing data from rats using the four fundamental reinforcement schedules: fixed interval (FI), fixed ratio (FR), variable interval (VI) and variable ratio (VR). Our results revealed interesting patterns in all experiment groups. In particular, the FI and VI groups exhibited well-organized clusters of data points. We calculated the fractal dimension out of these patterns and compared experimental data with surrogate data sets, that were generated by randomly shuffling the sequential order of original IRTs. This comparison supported the finding that patterns in ERM reflect the dynamics of the operant behaviors under study. We then built two models to simulate the functional mechanisms of the FI schedule. Both models can produce similar distributions of IRTs and the stereotypical 'scalloped' curve characteristic of FI responding. However, they differ in one important feature in their formulation: while one model uses a continuous function to describe the probability of occurrence of an operant behavior, the other one employs an abrupt switch of behavioral state. Comparison of ERMs showed that only the latter was able to produce patterns similar to the experimental results, indicative of the operation of an abrupt switch from one behavioral state to another over the course of the inter-reinforcement period. This example demonstrated the ERM to be a useful tool for the analysis of IRT accompanying intermittent reinforcement schedules and for the study of the non-linear dynamics of operant behavior.

Animals↗
PubMed1964

TEMPORALLY SPACED RESPONDING BY PIGEONS: DEVELOPMENT AND EFFECTS OF DEPRIVATION AND EXTINCTION.

In the first five or six sessions on a DRL 20-sec schedule of reinforcement there developed a stable performance characterized by a relatively constant conditional probability of occurrence (IRTs/op) of interresponse times (IRTs) of durations greater than 5 or 6 sec. Extinction and the level of deprivation changed both the overall rate of responding and the form of the function relating the duration of an IRT to its value of IRTs/op. The value of IRTs/op decreased more rapidly for short than for longer IRTs, resulting in the emergence of a finer discrimination of IRT duration.

Animals↗
PubMed1965

FREQUENCY DISTRIBUTION OF INTERRESPONSE TIMES DURING VI AND VR REINFORCEMENT.

A detailed analysis was made of the interresponse times (IRTs) of two rats under both a VI 40-sec and a VR 15-sec schedule. Except for the latency of the first response after a reinforcement, the mean IRTs of all further responses differed little. Similarly, the frequency distributions of the successive IRTs did not vary greatly, but were of no simple form. Sequential dependencies between successive IRTs were small, never accounting for more than 1% of the variance.

Rats↗
PubMed1982

Briefly delayed reinforcement: An interresponse time analysis.

Key-peck responding of pigeons was compared under VI or DRL schedules arranging immediate reinforcement and briefly (.5 sec) delayed reinforcement. Delays were either signaled by a blackout in the chamber, unsignaled, or unsignaled with an additional requirement that responding not occur during the .5 sec interval immediately preceding reinforcement (response delay). Relative to the immediate reinforcement condition, response rates increased during the unsignaled delay, decreased during the signaled delay, and were inconsistent during the response delay condition. An analysis of interresponse times (IRTs) under the different conditions revealed a substantial increase in the frequency of short (0 to .5 sec) IRTs during the unsignaled condition and generally during the response delay conditions compared to that during the immediate reinforcement baseline. Signaled delays decreased the frequency of short (0 to .5 sec) IRTs relative to the immediate reinforcement condition. The results suggest that brief unsignaled delays and, in many instances, response delays increase the frequency of short IRTs by eliminating constraints on responding.

Journal Article↗
PubMed1994

Continuous or split-course combined external and intracavitary radiotherapy of locally advanced carcinoma of the uterine cervix.

From 1974 to 1984, 442 consecutive patients with carcinoma of the uterine cervix (FIGO IIB: 139, IIIA:10, IIIB:221, IVA:72) were referred for combined intracavitary (IRT) and external radiotherapy (ERT). To improve local control and reduce late rectosigmoid morbidity the treatment strategy was changed from continuous (CRT) to split-course radiotherapy (SCRT) in 1978. Stage by stage the 5-year actuarial estimates of survival, local control, and late morbidity did not differ in relation to strategy. In the patients with tumours larger than 8 cm, the SCRT involved an increased dose in point B, a reduced dose in point A from the IRT, a lower total dose in point A, and a 34 days' prolongation of the total treatment time (TTT). The resulting 5-year actuarial local control rates were significantly lower compared with those after CRT. No difference of late severe morbidity was found except in IVA patients. In the patients with tumours between 4 and 8 cm, the SCRT involved a reduced dose in point A from the IRT, an increased total dose in point A and B, and a 50 days' prolongation of the TTT. In patients with stage IIB, the 5-year actuarial central local control rate was lower (p = 0.06), and the 5-year estimate of late severe morbidity significantly higher after SCRT compared with CRT. It is concluded that the increase of the dose in point B in the SCRT was insufficient to prevent the deleterious effect on local tumour control of either the lower dose from IRT in point A, or the prolonged TTT. The increase of the total dose in the SCRT may explain why the late morbidity was not reduced, and may suggest that the TTT is of no significant importance for the risk of late normal tissue damage.

Adult↗