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PubMed2001

Reproducibility of repeated measurements on healthy skin with Minolta Chromameter CR-300.

BACKGROUND/AIMS: In this report the reproducibility of measurements with the Minolta Chromameter CR-300 on healthy skin was investigated. METHODS: Intra- and inter-rater reproducibility, reproducibility with two instruments and repeated measurements with a 1 week time lapse were examined on healthy skin of 30 volunteers by means of intra-class correlation coefficients (ICC) and standard error of measurements (SEM). RESULTS: Results showed excellent values for ICC in all the four conditions. CONCLUSIONS: On the basis of these results we concluded that the instrument provides reliable information and can be used in comparative clinical trials.

Adult↗

PubMed1993

An assessment of the reliability and reproducibility of measurement of potential doubling times (Tpot) in human colorectal cancers.

An assessment has been made of the reproducibility of measuring tumour proliferation using in vivo iododeoxyuridine (IUdR) labelling and flow cytometry. The variation that occurs between different institutions (Paterson Institute for Cancer Research, Manchester and the Gray Laboratory, Northwood), different observers and different runs on the same flow cytometer have been measured on 139 samples from 53 patients with colorectal cancer. The results demonstrate that the IUdR technique for measuring tumour proliferation is reproducible. Correlations were seen between measurements of Tpot obtained by different individuals and on separate machines. However, direct comparisons of the measured parameters showed that there were highly significant differences in the values obtained between institutes and observers (P < 0.001). Despite these variations, there were still significant detectable differences in Tpot measurements between individual tumours (P < 0.001). Analysis of the results obtained by running the same samples on two separate occasions on the same machine showed that the technique was highly reproducible and that the staining procedure was stable. Eighty per cent of the samples were similarly assigned to either above or below the median Tpot value, regardless which observer/laboratory combination was utilised. These data suggest that large clinical trials using Tpot should employ a single centre and a single individual to prepare, run and analyse samples.

Adenocarcinoma↗

PubMed1997

Reproducibility of optic nerve head topographic measurements with the glaucoma-scope.

PURPOSE: Glaucoma is an optic neuropathy in which optic nerve changes are important in diagnosis and progression, because the visual field may remain normal even while the optic nerve is undergoing significant damage. Accurate methods to objectively document the appearance of the optic nerve are necessary. In order for an optic disc imaging system to be clinically useful for detecting change, its reproducibility must be established. METHODS: We measured the reproducibility of duplicate measurements in 59 eyes of 31 consecutive patients, grouped into glaucoma subjects (n = 29) and eyes with glaucoma (n = 30), with the 3.10 OIS Glaucoma-Scope. In order to simulate two visits on one day, sets of three optic disc images were obtained first, followed by a repeat set, and the best disc images of each (chosen by the computer) were compared. RESULTS: The coefficients of variation of duplicate measurements for glaucoma suspects and patients with glaucoma were respectively: vertical cup/disc (c/d) ratio, 6.3% and 3.47%; horizontal c/d ratio, 4.61% and 2.97%; c/d area, 3.29% and 1.37%; cup area, 1.82% and 1.72%; mean position (MP) disc, 13.3% and 10.42%; MP total, 10.1% and 13.2%. For three eyes the examination was not possible (opacification of posterior capsule, miosis). CONCLUSION: These results suggest that the 3.10 version of the OIS Glaucoma-Scope allows reproducible measurements in living eyes.

Adult↗

PubMed1996

Reproducibility of studies of peritoneal dialysis adequacy.

To assess the variability and reproducibility of dialysis adequacy clearance measurements (weekly Kt/V and weekly creatinine clearance/1.73 m2 BSA) in a given patient, 42 patients underwent three clearance studies in a one week period. The dialysis prescription was kept constant. There were 21 males with a group mean age of 49 +/- 15 years; 37 patients performed CAPD and 5 DAPD; the dialysis prescription was 6 to 12 liters/day; and 17 patients were anuric. To assess test variability within each patient, the coefficient of variation (CV) and the range were determined for each patient's three clearance values, and for the factors that determine those values. These were averaged to determine the mean patient variability (CV and range) of those measurements. The mean patient CV of the weekly Kt/V was 8.1%. The mean patient range of the weekly Kt/V was 0.30. Of the determinants of total Kt/V, the greatest variability (GV) existed in residual renal urea clearance at 35.4%, with moderate variability seen for peritoneal dialysis urea clearance at 7.0%, which was more a function of variability in D/P urea (CV = 6.3%) than variability in drain volume (CV = 4.1%). There was little variability in V (CV = 0.6%). Similar results were seen for the variability in weekly creatinine clearance measurements. We found that the day-to-day reproducibility of Kt/V measurements is limited, especially in patients with residual renal function, although day-to-day variability in D/P urea also affects Kt/V reproducibility in all patients. Values that fall into the borderline "adequate" range may need to be repeated when considering a patient's dialysis prescription. In addition, research that involves the measurement of Kt/V should utilize more than one collection to increase the reliability of those measurements.

Adult↗

PubMed2002

Clinical factors and clinical variation influencing the reproducibility of interocclusal recording methods.

OBJECTIVE: The reproducibility of clinical records of the occlusion was assessed in three dimensions using mounted casts. Three distinct areas were examined: 1) mandibular positions (intercuspal position (IP) or retruded contact position (RCP)), 2) materials used in recording the occlusion, 3) clinical variation. DESIGN: Interocclusal records were made in a random order of three patients: one fixed prosthodontics case, one removable partial denture case and one complete denture case, with two different types of waxes, record rims, two different brands of vinyl polysiloxanes and one irreversible hydrocolloid. SETTING: Private practice and Karolinska Institute, Huddinge, Sweden. SUBJECTS: One general dental practitioner and three voluntary patients. RESULTS: Point estimation of variance components indicate that 70-93% of the variation of the positions of the mounted casts are caused by: 1) clinical variation for all three cases and in three directions, 2) the influence of recording materials 0-29%, and 3) mandibular positions (IP/RCP) 0-11%. The ranges of the positions of the mounted casts were lower for the dentate case (0.04-1.39 mm) than for the partially dentate case (0.17-2.65 mm), which in turn was lower than those for the edentulous case (1.42-5.59 mm). CONCLUSION: Clinical variation seems to dominate the variation in positions of mounting casts when making interocclusal records, rather than mandibular position or the recording materials used. Therefore a dentist who makes one single interocclusal record cannot presume that it will reproduce the interocclusal relationship intended, which in the present study was most obvious for the edentulous case. The results showed that impression materials stabilised by a tray did not differ significantly from waxes and record rims concerning the reproducibility. Therefore the stabilised impression materials are an alternative, which also give additional advantages like reduction of appointments as well as superior accuracy.

Aged↗

PubMed2006

A simple, reproducible method for monitoring the treatment of tumours using dynamic contrast-enhanced MR imaging.

Dynamic contrast-enhanced MR imaging (DCE-MRI) may act as a biomarker for successful cancer therapy. Simple, reproducible techniques may widen this application. This paper demonstrates a single slice imaging technique. The image acquisition is performed in less than 500 ms making it relatively insensitive to respiratory motion. Data from phantom studies and a reproducibility study in solid human tumours are presented. The reproducibility study showed a coefficient of variation (CoV) of 19.1% for K(trans) and 15.8% for the initial area under the contrast enhancement curve (IAUC). This was improved to 16 and 13.9% if tumours of diameter less than 3 cm were excluded. The individual repeatability (the range within which individual measurements are expected to fall) was 30.6% for K(trans) and 26.5% for IAUC for tumours greater than 3 cm diameter. This approach to DCE-MRI image acquisition can be performed with standard clinical scanners, and data analysis is straightforward. For treatment trials with 10 patients in a cohort, the CoV implies that the method would be sensitive to a treatment effect of greater than 18%. The individual repeatability is well inside the 40% change shown to be important in clinical studies using this DCE-MRI technique.

Angiogenesis Inhibitors↗

PubMed1999

Reproducibility of detection of tyrosinase and MART-1 transcripts in the peripheral blood of melanoma patients: a quality control study using real-time quantitative RT-PCR.

In recent years, large discrepancies were described in the success rate of the tyrosinase reverse transcription polymerase chain reaction (RT-PCR) for detecting melanoma cells in the peripheral blood of melanoma patients. We present a quality control study in which we analysed the reproducibility of detection of tyrosinase and MART-1 transcripts in 106 blood samples from 68 melanoma patients (mainly stages III and IV). With this study, we aimed to improve insight in the reproducibility of a RT-PCR for the detection of (minimal) amounts of circulating melanoma cells. We performed two reverse transcriptions on each mRNA sample and performed tyrosinase and MART-1 nested PCRs in duplicate per cDNA sample. Thus, four tyrosinase and four MART-1 measurements were performed per blood sample. In our study, the majority of blood samples was negative for tyrosinase (80%) or MART-1 (66%). Only four samples were positive in all four determinations for tyrosinase and seven for MART-1. Variable results (1-3 times positive results) were obtained for tyrosinase and MART-1 in 16% and 27% respectively. MART-1 PCR had a better performance than tyrosinase PCR. Sensitivity increased when both markers were used. We reasoned that the low number of melanoma marker PCR-positive blood samples can be explained by differences in mRNA quality. By using real-time quantitative PCR, we found that this was not the case: amplification of porphobilinogen deaminase (PBGD), a low copy household gene, was not different in blood samples in which a melanoma marker was not detected from groups in which this marker was detected more or less consistently (1-4 times). When applying real-time quantitative PCR for tyrosinase and MART-1, we found that a low amount of SK-MEL-28 cell equivalents was present in the blood of melanoma patients, with a higher number of equivalents in the group with a consistently positive result. We conclude that low reproducibility of a repeated assay for the detection of circulating melanoma cells is not caused by differences in mRNA quality between the samples, but due to low numbers of amplifiable target mRNA molecules in the mRNA sample. Use of more than one marker and repetition of the assay will increase the probability of finding positive PCR results.

Adolescent↗

PubMed2005

Inter-device reproducibility of the scanning laser polarimeter with variable cornea compensation.

OBJECTIVE: To evaluate the interdevice reproducibility of retinal nerve fibre layer (RNFL) thickness measurements obtained with the commercially available GDx-VCC, a scanning laser polarimeter with variable (individualized) corneal compensation. METHODS: A prospective instrument validation study in which 13 GDx-VCC devices were tested. One eye each, from three normal subjects were used to test each of the devices, on the same day, by an experienced operator. Variability and reproducibility for each of five GDx parameters were calculated. RESULTS: For each of five tested GDx parameters, the coefficient of variation and 95% confidence interval range (microm), for the 13 devices, respectively, were: TSNIT avg: 5.1%, 3.84 microm; Superior avg: 5.3%, 4.82 microm; Inferior avg: 6.1%, 5.50 microm; TSNIT standard deviation: 8.6%, 2.92 microm; and nerve fibre indicator (NFI): N/A, 5.69. Item reliability (Cronbach's alpha) for the five GDx parameters are: TSNIT-Avg: 0.97, Sup-Avg: 1.00, Inf-Avg: 0.84, TSNIT-SD: 0.99, NFI: 0.99. CONCLUSIONS: With the commercially available GDx-VCC, our results indicate that RNFL measurements appear reproducible across devices.

Adult↗

PubMed2005

Accuracy of GDx variable corneal compensation polarization measurements in normal human eyes: effect of accommodation, cycloplegia, focus, pupil size, and eye selection on reproducibility.

PURPOSE: To evaluate the reproducibility of variable corneal compensation (VCC) and the effect of accommodation, cycloplegia, eye selection, focus, and pupil size on this measurement of polarization. METHODS: Using a GDx scanning laser polarimeter, multiple measurements of the VCC were obtained from each eye of 33 healthy, young adults under differing conditions. Pupil size and refraction were independently measured with a pupillometer and an autorefractometer. The effects of eye, instrument focus, pupil diameter, cycloplegia, and accommodation were statistically assessed. RESULTS: The reproducibility of a single retardation measurement and its axis, as determined by the standard deviations (SD) of repeated measurements, is +/-1.58 nm and 2.10 degrees , respectively. There is a difference in retardation between right and left eyes, of 5.26+/-9 nm, P=0.002. Increasing pupil size increases retardation. Cycloplegia or defocusing decreases retardation, and pharmacologically induced accommodation has no effect on retardation. CONCLUSIONS: The retardation and its axis are highly reproducible measurements when the pupil is of physiologic size and the GDx is properly focused. There is a consistent difference in VCC retardation between the paired right and left eyes. This difference may reflect equipment-induced measurement artefact and/or an anatomic asymmetry between the paired eyes of the subjects studied. Clinicians should be cautious when comparing interocular VCC measurements between paired right and left eyes and using data pooled from both eyes for age-adjusted, normalized standards.

Accommodation, Ocular↗

PubMed1997

Reproducibility of anthropometric and body composition measurements: the HERITAGE Family Study.

OBJECTIVE: To determine the reproducibility of anthropometric and body composition measures using the HERITAGE Family Study protocol. DESIGN: Anthropometric and body composition measures were obtained on three separate days within a 3-wk period at each of the four HERITAGE Clinical Centers. SUBJECTS: Sixty men and women representative of the HERITAGE subject population, 15 from each of four Clinical Centers. MEASUREMENTS: Anthropometric measures included eight skinfolds, three girths and one length; and body composition measures included stature, mass, hydrostatic weight, residual volume, and body density, from which relative fat, fat mass and fat-free mass were estimated. RESULTS: Reproducibility as determined by technical error, coefficient of variation, and intraclass correlations was very high for the total sample. For example, intraclass correlations for the total sample generally ranged from 0.95-0.99 for the anthropometric measures, and from 0.97-1.00 for the body composition measures. The results across Clinical Centers were in close agreement with each other and with the pooled data. CONCLUSIONS: The reproducibility of anthropometric and body composition measures using the HERITAGE Family Study protocol is sufficiently high that it should be possible to detect small changes in any of these measures and to determine the genetic basis of these changes consequent to a 20 wk endurance training program.

Adult↗

PubMed2001

Validity and reproducibility of ultrasonography for the measurement of intra-abdominal adipose tissue.

OBJECTIVE: We studied the validity and reproducibility of a new abdominal ultrasound protocol for the assessment of intra-abdominal adipose tissue. MEASUREMENTS: Intra-abdominal adipose tissue was assessed by CT, MRI, anthropometry and ultrasonography on a single day. By ultrasonography the distance between peritoneum and lumbar spine was measured using a strict protocol, including the location of the measurements, pressure on the transducer and respiration. All measurements were repeated after 3 months. RESULTS: The study population consisted of 19 overweight patients with a body mass index (BMI) of 32.9 kg/m(2) (s.d. 3.7), intra-abdominal adipose tissue on CT 140.1 cm(2) (s.d. 55.9), and a mean ultrasound distance of 9.8 cm (s.d. 2.5). There was a strong association between the CT and ultrasonographic measures: Pearson correlation coefficient was 0.81 (P<0.001). The correlation between ultrasound and waist circumference was 0.74 (P<0.001), the correlation between CT and waist circumference was 0.57 (P=0.01). Ultrasound appeared a good method to diagnose intra-abdominal obesity: the area under the ROC curve was 0.98. During the follow-up period of 3 months, the patients lost on average almost 3 kg of body weight. The correlation coefficient between changes in intra-abdominal adipose tissue assessed by CT and ultrasound was 0.74 (P<0.001). The correlation coefficient of the mean ultrasound distance assessed by two different sonographers at baseline was 0.94 (P<0.001), the mean difference 0.4 cm (s.d. 0.9), and the coefficient of variation 5.4%, indicating good reproducibility of the ultrasound measurements. CONCLUSIONS: The results of this validation study show that abdominal ultrasound, using a strict protocol, is a reliable and reproducible method to assess the amount of intra-abdominal adipose tissue and to diagnose intra-abdominal obesity.

Abdomen↗

PubMed1999

Reproducibility of salt sensitivity testing using a dietary approach in essential hypertension.

To investigate the reproducibility of salt sensitivity testing using a dietary approach, 30 essential hypertensive patients underwent salt sensitivity testing on an outpatient basis twice with a 6 month interval. At both tests casual and 24-h ambulatory blood pressure (24-h BP) was recorded on habitual diet, then after a 6-day period on a low salt diet (aiming at 50 mmol/day), and finally after a 6-day period on a high salt diet (supplementation with sodium chloride tablets aiming at 250 mmol/day). Subjects showing > or =10% increase in mean BP when changing from low to high dietary salt intake were classified as salt sensitive. Dietary salt intake was assessed as 24-h urinary sodium excretion. Based on 24-h BP recordings eight patients were characterised as salt sensitive (SS) and 22 as salt resistant (SR) in the first test, and three of the initial SS and 15 of the initial SR patients maintained their salt sensitivity status at the second test. Based on casual BP recordings 13 patients were characterised as SS and 17 as SR in the first test, and three of the initial SS and 13 of the initial SR patients maintained their salt sensitivity status at the second test. Thus, salt sensitivity status was reproducible in 60% when using 24-h BP, and in 53% when using casual BP measurements. There was no difference in baseline BP in dietary salt intake between the two tests. In the total study population, no significant correlation was found between the change in casual or 24-h BP during salt repletion in the first and second test. In conclusion casual and 24-h BP response to a 200 mmol/24h change in dietary salt intake is highly individual and varies over time. Characterisation of salt sensitivity using a dietary approach in out-patients is reproducible in only 53-60% of the patients.

Adult↗

PubMed2004

Reproducibility of nocturnal blood pressure fall in early phases of untreated essential hypertension: a prospective observational study.

A number of studies have shown that a smaller than normal nocturnal blood pressure (BP) decrease is associated with cardiovascular disease. However, no large prospective studies have examined the reliability of nocturnal dipping within individuals. The aim of our study was to investigate the short-term variability of nocturnal BP fall in a large cohort of patients with recently diagnosed essential hypertension. In all, 414 uncomplicated never treated hypertensive patients referred to our outpatient hypertension hospital clinic (mean age 46+/-12 years; 257 M, 157 F) prospectively underwent: (1). repeated clinic BP measurements; (2). routine examinations recommended by WHO/ISH guidelines; and (3). ambulatory BP monitoring (ABPM) twice within a 4-week period. Dipping pattern was defined as a reduction in the average systolic and diastolic BP at night greater than 10% compared to average daytime values. Overall, 311 patients (75.1%) showed no change in their diurnal variations in BP. Of the 278 patients who had a dipping pattern on the first ABPM, 219 (78.7%) confirmed this type of profile on the second ABPM, while 59 (21.3%) showed a nondipping pattern. Among 37 dipper patients with >20% of nocturnal systolic BP decrease (extreme dippers), only 16 (43.2%) had this marked fall in BP on the second ABPM. Of the 136 patients who had a nondipping pattern on the first ABPM, 92 (67.6%) confirmed their initial profile on the second ABPM, while 44 (32.4%) did not. Patients with reproducible nondipping profile were older (48+/-12 years) than those with reproducible dipping profile (44+/-12 years, P<0.05). These findings indicate that: (1). short-term reproducibility of nocturnal fall in BP in untreated middle-aged hypertensives is rather limited: overall, one-fourth of patients changed their initial dipping patterns when they were studied again after a few weeks; (2). this was particularly true for extreme dipping and nondipping patterns; (3). abnormalities in nocturnal BP fall, assessed by a single ABPM, cannot be taken as independent predictors of increased cardiovascular risk.

Adult↗

PubMed1999

Reproducible X-ray projection geometry in edentulous patients.

OBJECTIVE: To evaluate a novel fixation system for reproducible radiography in edentulous patients. METHODS: A conventional extra-oral fixation system was modified with a filmholder and adjustable scales. For measuring reproducibility and angulation errors two rods and two balls were fixed on the alveolar crests of the maxilla and the mandible and angular variations were measured. One hundred radiographs of a conventional phantom were taken by one of the authors and by ten dental students. The angular disparity was calculated and intra- and interoperator precision determined. RESULTS: The average time taken to assemble the fixation system was 4 min. The 95% confidence interval for precision of the single operator was less than 2.5 degrees in both the maxilla and mandible. The 95% confidence interval for precision of the ten students was less than 2.2 degrees for the maxilla and 2.7 degrees for the mandible. There was no significant difference (P>0.05) in interoperator precision. CONCLUSION: The novel extra-oral fixation system appears to be a potential means of obtaining reproducible radiographs of edentulous patients.

Humans↗

PubMed1991

Long-term reproducibility of Borg scale estimates of breathlessness during exercise.

1. The intensity of breathlessness in normal subjects during exercise was measured on seven occasions over a 40-week study period to assess the long-term repeatability of Borg scale estimates of breathlessness. 2. In all subjects there was a significant correlation (P = 0.0001) between breathlessness and minute ventilation. Minute ventilation measured at each work rate did not differ between the seven exercise tests (P greater than 0.05). 3. There was no significant difference between the mean Borg scores (measured with respect to a given level of ventilation) in 5 of the 7 test weeks (P greater than 0.05). The slope of the relationship Borg score/minute ventilation did not differ between the seven exercise tests (P greater than 0.05). 4. Breathlessness estimation was highly reproducible both after 1 week and after 40 weeks of the study (both P greater than 0.05). 5. The duration without testing between consecutive tests did not affect reproducibility: the mean Borg score was as equally reproducible after an interval of 22 weeks without testing as after an interval of 1 week (P greater than 0.05). 6. The Borg scale provides a reliable technique for studying the sensation of breathlessness over extended time periods.

Adult↗

PubMed1991

Short-term reproducibility of a mental arithmetic stress test.

1. To evaluate the short-term reproducibility of heart rate, oscillometrically determined blood pressure, antecubital venous plasma catecholamine concentrations and subjective responses to strictly standardized mental arithmetic, we performed two identical tests 1 h apart in 14 young, healthy and normotensive male subjects (age 22-35 years). 2. Heart rate and blood pressure responses to the two stress tests were highly correlated, when expressed both as correlations between levels attained during stress (rs greater than 0.80 throughout) and as absolute reactivity measures (all rs greater than 0.75). Also, subjective stress responses were highly correlated, when considering both levels during stress and reactivity (r = 0.97 and r = 0.85, respectively). Stress levels of catecholamines were correlated, but the change scores (reactivity) were unrelated. 3. The measurement error SD for heart rate was 2.6 and 3.0 beats/min for reactivity and stress levels, respectively. The corresponding SD for blood pressure ranged between 2.7 and 4.4 mmHg. Subjective stress experience showed an SD of a similar magnitude. The responses of plasma catecholamine concentrations were subject to considerable variability. 4. It is concluded that haemodynamic and subjective stress responses and stress levels during the mental arithmetic stress test show acceptable reproducibility and high test-retest correlations. However, stress-induced changes in venous plasma catecholamine concentrations show low reproducibility.

Adult↗

PubMed1996

Reproducibility of heart rate variability measures in patients with chronic heart failure.

1. In patients with chronic heart failure, heart rate variability is reduced with relative preservation of very-low-frequency power (< 0.04 Hz). Heart rate variability has been measured without acceptable information on its stability and the optimal recording periods for enhancing this reproducibility. 2. To this aim and to establish the optimal length of recording for the evaluation of the very-low-frequency power, we analysed 40, 20, 10 and 5 min ECG recordings obtained on two separate occasions in 16 patients with chronic heart failure. The repeatability coefficient and the variation coefficient were calculated for the heart rate variability parameters, in the time-domain (mean RR, SDRR and pNN50), and in the frequency-domain: very low frequency (< 0.04 Hz), low frequency (0.04-0.15 Hz), high frequency (0.15-0.40 Hz), total power (0-0.5 Hz). 3. Mean RR remained virtually identical over time (variation coefficient 8%). The reproducibility of time-domain (variation coefficient 25-139%) and of spectral measures (variation coefficient 45-111%) was very low. The stability of the heart rate variability parameters was only apparently improved after square root and after log transformation. 4. Very-low-frequency values derived from 5 and 10 min intervals were significantly lower than those calculated from 40 and 20 min intervals (P < 0.005). Discrete very-low-frequency peaks were detected in 11 out of 16 patients on the first 40, 20 and 10 min recording, but only in seven out of 16 when 5 min segments were analysed. 5. The reproducibility of both time or frequency-domain measures of heart rate variability in patients with chronic heart failure may vary significantly. Square root or log-transformed parameters may be considered rather than absolute units in studies assessing the influence of management on heart rate variability profile. Recordings of at least 20 min in stable, controlled conditions are to be recommended to optimize signal acquisition in patients with chronic heart failure, if very-low-frequency power in particular is to be studied.

Chronic Disease↗

PubMed1997

Comparison between reproducibility and sensitivity of muscle sympathetic nerve traffic and plasma noradrenaline in man.

1. Although plasma noradrenaline and muscle sympathetic nerve traffic have been shown to be suitable markers of sympathetic activity in man, no study has systematically compared the reproducibility and sensitivity of these two indices of adrenergic tone. 2. Reproducibility data were collected in 10 subjects, in whom plasma noradrenaline was assessed by HPLC on blood samples withdrawn from an antecubital vein and efferent postganglionic muscle sympathetic nerve activity was measured by microneurography from a peroneal nerve, together with arterial blood pressure (Finapres technique). Measurements were obtained in a first session (session 1), 60 min later (session 2) and after 14 days (session 3). While muscle sympathetic nerve activity values recorded in the three different experimental sessions were closely and significantly correlated with each other (r always > 0.90, P < 0.001), noradrenaline showed a less significant correlation between sessions 1 and 2 (r = 0.71, P < 0.05) or no correlation between sessions 1 and 3 (r = 0.45, P not significant). 3. Sensitivity data were collected by evaluating muscle sympathetic nerve activity and noradrenaline values in three different age groups (young, middle-age and old subjects, n = 18), in three groups with different blood pressures (normotensive, mild and severe hypertensive subjects, n = 30) and in a group of eight subjects before and after a physical training programme, i.e. conditions known to increase or reduce sympathetic cardiovascular drive. Muscle sympathetic nerve activity was significantly increased by aging and hypertension, and reduced by physical training. The noradrenaline changes were much less marked and consistent. 4. These data suggest that muscle sympathetic nerve activity has a greater short- and medium-term reproducibility than noradrenaline. In several conditions known to modify sympathetic cardiovascular drive muscle sympathetic nerve activity also appears to change more clearly than noradrenaline.

Adolescent↗