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PubMed2000

Validation of a fatigue impact score in primary biliary cirrhosis: towards a standard for clinical and trial use.

BACKGROUND/AIMS: Fatigue is the commonest symptom of the chronic liver disease primary biliary cirrhosis (PBC). PBC is increasingly being diagnosed earlier in its natural history at a stage when concerns about progression to liver failure may be less prominent than current symptoms. The importance of symptomatic treatment is therefore increasingly being recognised. Research into the aetiology and treatment of fatigue in PBC has been hampered by the lack of relevant, reproducible measures of fatigue severity. The aim of this study was to validate the Fisk Fatigue Severity Score (FFSS), a measure of the impact of fatigue on daily living, for use in PBC and to use the FFSS to study the severity and correlates of fatigue in this condition. METHODS: Fifty-eight patients with PBC and 31 matched control patients attending hospital for nonhepatic disease were studied. The reproducibility of FFSS was assessed over periods from 1 hour to 1 month. Fatigue, as measured by FFSS, was compared in PBC patients and controls. The severity of fatigue in the patients with PBC was correlated with other symptoms and with established biochemical and histological markers of severity. RESULTS: The FFSS questionnaire was acceptable to patients and had reasonable intra-observer variation (coefficient of reproducibility 13% of mean value at 1 hour). The FFSS was more reproducible than a visual analogue scale. FFSSs varied over 4 weeks by up to 36%. Median FFSS's were 2.3 times higher in PBC patients than controls (p<0.005). There were no associations between FFSS and patient age, disease duration, or histological or biochemical markers of severity. CONCLUSIONS: The FFSS is a highly acceptable, internally consistent and reproducible measure of fatigue severity in PBC. We advocate its use in clinical assessment of patients, in studies of the aetiology of fatigue in PBC and, most importantly, in therapeutic trials of symptomatic treatment.

Clinical Trials as Topic↗

PubMed1996

Left ventricular regression equations from single plane cine and digital X-ray ventriculograms revisited.

For the assessment of left ventricular volume from X-ray ventriculograms, widely known regression equations are used to correct for the irregular shape of the left ventricular lumen and the presence of the papillary muscles and trabeculations. These regression equations were derived in the late nineteen sixties and seventies. With all the changes in X-ray technology that have taken place over the past 20-30 years, the question was raised whether these regression equations were still valid. Therefore, 23 left ventricular casts of known volume were imaged in RAO20, RAO30 and RAO40 angiographic views and recorded on 35 mm cinefilm as well as in digital format. All the frames were traced manually by two observers and the volumes calculated by the Area Length and Simpson Rule approaches. The following conclusions could be drawn: inter- and intra-observer variations were small (systematic differences < 1.5 ml; random differences < 2.9 ml) and statistically not significant; the regression equations are virtually the same for the RAO20, RAO30 and RAO40 views under the different circumstances; the Area Length method was associated with slightly smaller values for the standard-error-of-the-estimate (SEE) suggesting a slight preference for this approach versus the Simpson Rule; significant differences were found between the cinefilm and digital regression equations; and the following new regression equations are proposed, which indeed differ significantly from the earliest proposals and less from the monoplane formulas proposed by Kennedy & Lange in the 1970s: [table: see text]

Angiography, Digital Subtraction↗

PubMed1991

The mammographic parenchymal patterns of nulliparous women and women with a family history of breast cancer.

One-hundred-and-thirteen mammograms of nulliparous women and 44 mammograms of women with a family history of breast cancer were graded according to Wolfe's parenchymal pattern classification. These were compared to 437 mammograms of women without these risk factors. Mammograms were read by two independent observers in order to evaluate inter- and intra-observer variation. The interobserver variation was reduced from 17% to 5% by combining high risk patterns (P2 and DY) and low risk patterns (N1 and P1). A significantly higher proportion of high risk patterns was found in nulliparous women compared to parous women (P less than 0.01). The proportion of high risk patterns decreased significantly with the number of children (P less than 0.01). Women with a family history of breast cancer had almost the same parenchymal patterns as women without a family history. In conclusion, while nulliparity and family history are recognized risk factors for developing breast cancer, only nulliparity would appear to influence the mammographic parenchymal pattern. This probably reflects the different mechanism by which the two factors affect breast tissue.

Breast Neoplasms↗

PubMed1999

How does a change in the administration method affect the reliability of the COOP/WONCA Charts? World Organization of National Colleges, Academies and Academic Associations of General Practitioners/Family Physicians.

BACKGROUND: An interviewer is often needed to administer the COOP/WONCA Charts to Chinese patients, and this may affect the reliability of results. OBJECTIVES: We aimed to find out the reliability of the COOP/WONCA Charts administered by an interviewer, and whether a change in the interviewer or administration method would affect the results. METHODS: We carried out a cross-sectional test-retest study on 487 Chinese adult patients attending a family medicine clinic in Hong Kong. The COOP/WONCA Charts were administered by the same interviewer, two different interviewers or self-completion and interviewer administration, on test and retest. The random, inter-observer and inter-method variances were compared with the inter-subject variance. The reliability coefficient of each COOP/WONCA Chart was calculated for each method of administration. RESULTS: Random errors could change the scores by 0.57-1.04, inter-observer variations could change the scores of four charts by 0.72-0.80, and a change in the method could change the physical fitness score by 1.79 and the daily activities score by 1.31, on a five-point scale. The reliability coefficients of the six COOP/WONCA Charts were 0.68-0.92 for one interviewer, 0.59-0.82 for two interviewers and 0.46-0.81 for two methods. CONCLUSION: The Chinese COOP/WONCA Charts were reliable in detecting real differences when administered by an interviewer. A change in the method of administration significantly decreased the reliability of the results. The use of more than one method of data collection in the same survey should be discouraged.

Adult↗

PubMed1994

A histological semiquantitative scoring system for evaluation of hepatic fibrosis in needle liver biopsy specimens: comparison with morphometric studies.

The evaluation of hepatic fibrosis on histological sections is of great interest for the staging and follow-up of chronic liver disease. Because no reliable scoring system is yet available, we have designed a semiquantitative scoring system in which the four main sites of fibrotic deposit--centrilobular vein, portal tract and perisinusoidal space, together with width and number of septa when present--are analyzed. These different items have been previously settled from comparison with morphometric measurements to evaluate surface density of total collagen performed on the same liver needle biopsy specimens stained with picro-sirius. The score has been tested on samples from 200 consecutive patients with various liver diseases and compared with the surface density of total collagen and Knodell scoring system. For observer variation study, the features by three independent pathologists were coded on 20 cases. There was a good interobserver (Kendall's tau-b = 0.75) and intraobserver (tau-B = 0.73) reproducibility. Each component of the fibrosis scoring system and total collagen surface density were significantly linearly related (one-way polynomial analysis, p < 10(-4); the correlation between semiquantitative scoring system and surface density of total collagen was 0.73 (p < 10(-5). Our semiquantitative scoring system, simple and reproducible, describes both liver architecture and fibrotic deposit. It is better related to morphometric measurement of fibrosis than each of its constituents or than the fibrosis item of the Knodell scoring system. It represents a reliable and convenient method for fibrosis evaluation, which is mandatory for clinical use.

Analysis of Variance↗

PubMed1998

Reliability of Doppler ultrasound in follow-up studies.

PURPOSE: To evaluate the reliability of repeat Doppler US measurements. MATERIAL AND METHODS: Nine radiologists conducted two sets of Doppler US measurements on a healthy volunteer, with a time interval of 9 months. Peak systolic velocity (PSV), resistance index (RI), and pulsatility index (PI) were measured 10 times in 4 arteries. RESULTS: There was considerable intra- and inter-observer variation both at baseline and 9 months later. The PSV values from the carotid artery varied from 0.27 m/s to 1.95 m/s in February and from 0.22 m/s to 1.38 m/s in November. The RI values from the renal artery ranged from 0.44 to 0.71 in February and from 0.41 to 0.67 in November. The results of the 9-month follow-up varied markedly too. Best reproducibility was achieved by highly experienced radiologists both at baseline and 9 months later. CONCLUSION: The short-term and long-term reliability of Doppler US was poor when the measurements were performed by a heterogeneous group of radiologists. The RI and PI measurements were somewhat more reliable than the PSV measurements and are recommended for use in follow-up studies.

Adult↗

PubMed2004

Multidetector CT angiography versus digital subtraction angiography for aortoiliac length measurements prior to endovascular AAA repair.

PURPOSE: To assess observer variation between calibrated-catheter digital subtraction angiography (DSA) and software-enhanced multidetector computed tomography angiography (CTA) in measuring vessel length prior to endovascular aortic aneurysm repair (EVAR). METHODS: Thirty patients (25 men; mean age 65 years, range 61-85) scheduled for EVAR underwent CTA in 4x2-mm collimation using advanced vessel analysis software. CTA measurements were performed twice by 2 blinded readers in random order with at least a 4-week interval between readings. Nine patients were found unsuitable for endovascular repair after the CTA, so DSA was performed in 21 patients for morphometric evaluation of the abdominal aorta and the iliac arteries. The following segments were measured: H1 (aneurysm neck), H2 (lower renal artery to distal aspect of the aneurysm), H3 (lower renal artery to aortic bifurcation), and H4a/H4b (lower renal artery to iliac bifurcations). Length measurements on DSA were made by (1) following the catheter path in the aortic lumen and (2) dividing tortuous vessel anatomy into segments and measuring each segment along an idealized centerline. Addition of the various segments allowed comparison with data obtained from CTA measurements. RESULTS: CTA was performed with good intraobserver agreement for all length parameters except H3 in reader 2 (p<0.05). While good interobserver agreement was demonstrated for CTA over long aortoiliac distances (H4a, H4b), higher interobserver agreement was obtained with DSA for shorter segments (H1, H2). Considerable differences were observed between CTA and DSA for the lengths H2 and H4b. CONCLUSIONS: CTA produces better intra and interobserver correlations in measuring vessel length than DSA. It has the potential to replace DSA as an imaging method before EVAR.

Aged↗

PubMed1993

Evaluation of the ARI program: a health facility survey in Simbu, Papua, New Guinea.

The purpose of this health facility survey was to evaluate how the ARI (Acute Respiratory Infection) Program actually works in an everyday, non-research setting. We surveyed 33 clinics and aid posts, including 223 children with ARI and 104 health workers. In this primary health care setting, health workers diagnosed 37% of ARI cases as pneumonia, compared to 69% in the same children assessed independently by trained ARI surveyors using Papua New Guinea case management, which defines fast breathing as > or = 40 per minute for children 1 month to 5 years of age. Agreement between health workers and surveyors was reasonably good (kappa > or = 0.6) for the history of symptoms, but was poor (kappa < 0.3) for diagnoses, treatments and signs such as respiratory rate (RR) and chest indrawing. Health workers counted the RR in only 14% of cases in the survey. In essence, we found that health workers in Simbu are not practising ARI case management. We conclude that case management guidelines which define fast breathing as a rate of > or = 40 per minute classify too many obviously well children as pneumonia. Furthermore, we encountered difficulties in measuring RR accurately, and documented marked inter-observer variation in this setting. Consequently, we are concerned about the ARI Program's excessive reliance on RR and rigid protocols at the expense of clinical sense. Case management guidelines developed for aid post orderlies or village health workers may need to be modified, or used differently by experienced nurses at health centres, who recognize sick children better than by following a standardized protocol. Despite better overall ARI knowledge and practice by nurses, we could demonstrate an impact of the ARI Training Program only on community health workers (CHWs). In order to improve ARI clinical practice, we recommend that the ARI Program in PNG initiates regular on-site clinical supervision of nurses and CHWs at health centres.

Acute Disease↗

PubMed1998

Clinical validation of self-reported osteoarthritis.

OBJECTIVE: To evaluate the use of a postal survey to detect subjects in the community with osteoarthritis (OA) and the ability of metrologists to detect clinical OA. METHODS: Questionnaires were posted to a random sample of residents of the Northern Sydney Health Area, aged 45-64 years old, asking for details of musculoskeletal complaints and diagnoses. A questionnaire definition of OA was made if 'osteoarthritis' was reported or 'degenerative arthritis', 'joints wearing' out together with pain in joints during the previous 6 months. Hands, hips, and knees of 106 subjects were examined by one of two trained metrologists according to ACR clinical criteria for OA. A second subsample was examined by two metrologists and two rheumatologists independently to test for inter-observer variation. Data were analyzed for percentage agreement and concordance using the kappa statistic. RESULTS: After two mailouts, 59% responded (526 males and 796 females). Definite OA (excluding spine alone) was reported by 52 males (10%), 155 females (19.5%) and possible OA by 62 males (11.8%), 164 females (20.6%). Following examination, 81% of self-reported 'definite' OA was confirmed, while 57% of 'possibles' and one self-reported 'negative' were determined to have clinical OA. Reporting of specific joint OA was less reliable than the highly reliable self-reporting of general OA. Good agreement was demonstrated between rheumatologists and metrologists in the clinical diagnosis. CONCLUSION: Postal questionnaires have the potential to detect OA in the community. The clinical diagnosis can be confirmed by a trained metrologist. Further evaluation of this instrument is warranted in other populations.

Australia↗

PubMed2001

Evaluating HER2 amplification and overexpression in breast cancer.

The development of Herceptin (Trazumatab) makes testing for HER2 status important for choosing optimal therapy in breast cancer. This study addresses the precision, accuracy, and reproducibility of HER2 assays. HER2 was assessed retrospectively by immunohistochemistry (IHC) with Dako 'Herceptest', by IHC with the monoclonal antibody CB11, and by fluorescence in situ hybridization (FISH, PathVysion), in a series of 216 formalin-fixed breast carcinomas including 191 for which quantitative HER2 data from radioimmunohistochemistry (Q-IHC) were available. All tests were scored independently by two observers. Positivity rates varied between Herceptest (12.6%), FISH (19.4%), and CB11 IHC (28.5%). Kappa values showed that IHC-based tests were more susceptible to inter-observer variation (kappa=0.67 and 0.74 for Herceptest and CB11, respectively) than FISH (kappa=0.973). Overall test accuracy (see the Materials and methods section) for CB11 IHC (83.8%) was lower than Herceptest (87.4%) or FISH (93.2%). FISH predicted p185 HER2 overexpression (determined by Q-IHC) better (concordance index C.Ind. 0.90) than CB11 IHC (C.Ind.=0.85) or Herceptest (C.Ind.=0.81). Of 42 cases with gene amplification by FISH, 67% were positive in the Herceptest (2+ or 3+) vs. 83% with CB11. Of 174 cases negative by FISH, 96% were negative in the Herceptest and 68% with CB11. In conclusion, FISH is the most accurate, reproducible, and precise predictor of HER2 overexpression in routine diagnostic laboratories.

Antibodies, Monoclonal↗

PubMed1996

Predictive value of signs and symptoms in the diagnosis of subarachnoid hemorrhage among stroke patients.

Clinical diagnosis of subarachnoid hemorrhage (SAH) is frequently misdiagnosed with intracerebral hemorrhage (ICH) or cerebral infarction (CI), which delays appropriate referral. This study was undertaken to create a clinical index to select, among stroke patients, those with the highest probability of having a SAH. Clinical data of patients with acute stroke were evaluated with the X2 and the Fisher exact test; a p value < 0.05 was considered significant. Significant variables were included in a "log-lineal regression analysis" where those with an odds ratio (OR) 95% confidence limits not including the unit were considered to construct an index using the odds ratio coefficient (C). The results indicated that of 197 records which were included, 22 cases of SAH and 175 of ICH or CI were demonstrated. Kappa coefficients for observer variation in clinical data retrieval was 0.91. After "log-lineal regression analysis" was carried out the following variables were significant: neck stiffness (C = 3, OR = 21); lack of focal neurologic signs (C = 2, OR = 6.88); and age < or = 60 years (C = 1.5, OR = 4.35). A fourth variable, seizures (C = 1, OR = 3.25), was marginally significant (p = 0.07), but added predictive value to the index. The positive predictive values of the sum of the coefficients were: 0 = 0%; 1-2 = 3%; 2.5-3.5 = 21%; 4-5 = 40%; 6.5 = 75%; 7.5 = 100%. In conclusion, when a stroke patient shows neck stiffness, or any combination of young age, lack of focal neurologic signs or seizures (a score > or = 2.5, the index has a 91% sensitivity and 82% specificity), he/she must be referred to a tertiary care center.

Adolescent↗

PubMed1999

Evaluation of pneumonia diagnosis in intensive care patients.

The aims of this study were to investigate the frequency of bronchopneumonia diagnosed by histological criteria among autopsied intensive care unit (ICU) patients and to compare these with rates of pneumonia diagnosed by conventional clinical methods. The study material comprised 141 autopsied ICU patients from 7 ICUs in university hospitals in Copenhagen from a 1-y period. A total of 20 lung tissue specimens were sampled from each patient and the histopathological diagnoses were classified as no, mild, moderate or severe bronchopneumonia. Inter-observer variation was calculated using kappa statistics. Demographic data and diagnoses of pneumonia were registered from the patient files. Twenty-six percent of the patients had pneumonia diagnosed whilst in the ICU. Histological evidence of pneumonia, found for every second patient, was regarded as the gold standard. Diagnosis of pneumonia in the ICU had a sensitivity of 29% and if diagnoses of pneumonia during the month before ICU-admission were included, a sensitivity of 60% was found. Specificity for pneumonia diagnosed in the ICU was 77%. The percentage of all ICU-patients with pneumonia was calculated to be between 36% and 56%, depending on the extent of excess mortality attributable to pneumonia. Pulmonary segments with histologically diagnosed pneumonic lesions were distributed diffusely, although the upper segments tended to be affected less. Nearly all patients had other histopathological findings than bronchopneumonia. The reliability coefficient among the 6 pathologists was found to be moderately good (kappa = 0.45).

Adolescent↗

PubMed2001

Using CT and cholangiography to diagnose biliary tract carcinoma complicating primary sclerosing cholangitis.

OBJECTIVE: The objective of our study was to determine the value of CT and cholangiography for diagnosing biliary tract carcinoma complicating primary sclerosing cholangitis. MATERIALS AND METHODS: One hundred thirteen abdominal CT examinations and cholangiograms in 45 patients with primary sclerosing cholangitis, including 18 patients with established biliary tract carcinoma, were analyzed for tumor. Four radiologists who were unaware of the presence or absence of carcinoma rated each study as to the probability of malignancy. Receiver operating characteristic curve analysis was used to assess the diagnostic performance of CT and cholangiography, the value of imaging signs, and the degree of inter-observer variation in interpretation. Sensitivity and specificity values were calculated. RESULTS: CT outperformed cholangiography in the detection of carcinoma. The average area under the receiver operating characteristic curve was 0.82 for CT and 0.57 for cholangiography (p = 0.003). Sensitivity and specificity for detecting carcinoma using CT were good, with average values of 82% and 80%, respectively. Average sensitivity and specificity for cholangiography were 54% and 53%, respectively. The most reliable sign of tumor on CT was a discrete mass. Progressive biliary dilatation on sequential studies was the most useful sign on cholangiography. Interobserver agreement assessed using the Cronbach alpha was fair for cholangiography and good for CT. CONCLUSION: CT provides good sensitivity and specificity and significantly outperforms cholangiography in detecting biliary tract carcinoma complicating primary sclerosing cholangitis. Despite limitations, CT and cholangiography provide useful information not otherwise available in the treatment of patients with primary sclerosing cholangitis.

Adult↗

PubMed1995

Reproducibility of the WHO classification of glomerulonephritis.

The inter-observer variation of the WHO classification of glomerulonephritis (GN) was studied using Kappa statistics. One hundred renal biopsies were selected with almost equal representation of the following types of GN: minimal change nephropathy, membranous GN, focal proliferative GN, diffuse mesangial proliferative GN, endocapillary GN, membranoproliferative GN, and crescentic GN. Slides stained with silver-methenamine and PAS-hematoxylin were circulated among the members of the panel, who made their diagnoses without knowing those of the other participants and without knowledge of the clinical conditions. There was a very good overall diagnostic agreement of 0.67 with a Kappa value of 0.61, figures which compete very well with other diagnostic systems analysed with Kappa statistics. Analysing the single types of GN, we found that the highest Kappa values were obtained for crescentic GN (0.81), endocapillary GN (0.79) and membranous GN (0.74) and the lowest Kappa values for membranoproliferative GN (0.40) and diffuse mesangial proliferative GN (0.44). Basically, the international classification of GN is founded upon light microscopy. Our results demonstrate that this system works generally well. The diagnostic reproducibility of the types with less satisfactory Kappa values can be expected to be improved by including immunopathology and electron microscopy.

Biopsy↗

PubMed2004

Precision and accuracy of the bedside examination in detecting an ejection fraction of less than 40% following acute myocardial infarction.

BACKGROUND: Left ventricular function is the most important determinant of prognosis following myocardial infarction. METHODS: A prospective analytical cohort study of 33 cardiac care unit survivors of acute myocardial infarction was performed to assess the accuracy, reproducibility and observer variation of the bedside Valsalva response in predicting an ejection fraction (EF) less than 40%. RESULTS: Agreement between physicians for the clinical Valsalva response was excellent (kappa coefficient 0.75), as was the comparison between physicians' clinical response to the Finapres (Ohmeda, USA) hemodynamic response (weighted kappa=0.85). The EF was significantly higher among patients with a normal Valsalva response (56.9%) than in patients with either an absent overshoot (48.4%) or a square wave (28.3%) response (P<0.001). Physicians were very accurate at estimating whether the EF was greater or less than 40%. In 40 of 66 situations, the clinicians were confident, based on the clinical examination and the Valsalva response, that the EF was either greater or less than 40%. In these situations, agreement (95.0%) and kappa (0.89) were both excellent. When all patients were considered, the degree of agreement (90.8%) and kappa (0.80) diminished slightly. A square wave response had poor sensitivity (37.5%) but excellent specificity (92.7%), whereas any abnormal response had excellent sensitivity (91.7%) but poor specificity (54.8%). CONCLUSION: Compared with many other aspects of the clinical examination, the bedside Valsalva manoeuvre has acceptable degrees of interobserver variability. A normal response tends to rule in an EF of greater than 40%, whereas a square wave response rules out an EF of greater than 40%. This simple bedside manoeuvre may be useful in predicting low EF following acute myocardial infarction.

Adult↗

PubMedDate not supplied

PAPNET. The human and other dimensions.

OBJECTIVE: To study the effect of specimen preparation and observer variation on the accuracy of interpretation of PAPNET images. STUDY DESIGN: The PAPNET scanner makes use of conventional Papanicolaou-stained smears and presents the cytologist with pictures of selected "abnormal" cells. This minitrial was designed to investigate the human variability in different grades of personnel and to consider any problems caused by the use of conventional smears. RESULTS: The personnel involved consisted of a consultant cytopathologist, a senior chief medical laboratory scientific officer and two senior cytotechnologists, one from another laboratory. Experience with the system ranged from six months to a few years. The best interobserver agreement was found between the senior chief and the senior technologist, who worked in the same laboratory. Majority agreement with the "gold standard" (at least three out of four) was highest for the extremes of "negative" and "high grade" smears. Three high grade smears were "missed" due to the quality of the smears and scantiness of "abnormal" cells. CONCLUSION: Although fatigue in screening is reduced by the interactive mode, it does not overcome the subjectivity of human examination both in review of the dat tape and in microscopic examination of selected cells on the slides. Experience with the method is important, and different background experiences will have an effect. The technical quality of the smear is important since the automated scanner cannot be expected to select abnormal cells if they are absent or obscured for any reason. A monolayer may be the solution, although at greater cost.

Diagnosis, Computer-Assisted↗

PubMed2007

A dynamic analysis of GP visiting in Ireland: 1995-2001.

This paper examines the determinants of GP visiting in Ireland, using panel data from the Living in Ireland Survey from 1995-2001. While cross-sectional studies provide important information on GP visiting patterns at a certain point in time, with panel data we can also control for unobserved individual heterogeneity, as well as identify whether it is the same individuals who consistently visit their GP year on year, or whether there is more mobility in visiting. We therefore estimate dynamic models of GP utilisation, and attempt to decompose the observed variation in GP visiting into components attributable to observed individual characteristics, unobserved individual heterogeneity and state dependence.

Adult↗

PubMed1988

Quantitative electromyography of the masticatory muscles of Pteropus giganteus (Megachiroptera).

Mastication has been studied by cinematography and quantitative electromyography while flying foxes, Pteropus giganteus, were freely feeding on standardized pieces of apple, soaked raisin, and banana. The primarily orthal mandibular movements are caused by mainly bilaterally symmetrical firing of all the masticatory muscles. Asymmetric activity in the superficial and deep masseter and medial pterygoid causes slight protrusion early in opening. Slight lateral deviations at the end of opening and at the start of closing are caused by asymmetric and asynchronous activity in the pterygoids and digastrics, and by asynchronous firing of the deep temporalis and zygomaticomandibularis. Food consistency affects movement characteristics as well as characteristics of muscular activity. In this study electromyograms were digitized and the number of spikes and mean amplitude per interval (set by the filming rate) recorded. Although a significant correlation exists between descriptors, the product thereof appears to be the best predictor of certain kinematic variables (cycle length and maximum excursion of the mandible). On the other hand, the changes in magnitude of muscular activity as a function of the position of a cycle in the reduction sequence and as a function of food consistency are more translated in a variation of the mean amplitude than in a variation of the number of spikes per interval. Observed variation differs among muscles studied. It is most apparent in the superficial and deep masseter and least in the temporalis and zygomaticomandibularis. Late cycles of apple and raisin mastication are long and exhibit large gapes but almost no anterior movement. The adductor activity frequently shows a synchronized, pulsatile pattern leading to an unfused tetanus.

Animals↗