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PLASMA CATECHOLAMINE ASSAYS
876 PLASMA CATECHOLAMINE ASSAYS
SIR,-Dr Mendelsohn and his colleagues (March 1, p. 492) cite their failure to find an increase in plasma catecholamines as evidence against stimulation by aagiotensin of the sympathetic nervous system. As they admit, there has been considerable controversy over the role of sympathetic activity in the genesis of essential hypertension. All the more important, then, that such studies should employ reliable and credible catecholamine assays. Mendelsohn’s values for both adrenaline and noradrenaline (double isotope method) are several times higher than values reported by those using the more sensitive single isotope assays,’-3 which in turn accord with values found by the entirely different methodology of high-performance liquid chromatography and electrochemical detection.4,5 (The presentation by Mendelsohn et al. of noradrenaline values in "pg/ml" was presumably a misprint for "ng/ml".) The method used by Mendelsohn et al. was initially used in the diagnosis of phaeochromocytoma, where circulating levels of catecholamines may be several times higher than normal. Where this is not the case, it is impossible, using a 14C-methyl donor (as is necessary in the double isotope assay used) to detect circulating adrenaline -in most individuals. Even if the 0-3pmol of adrenaline per ml of "average" plasma6were completely methylated and the ’4C-metanephrine so formed recovered 100%, the maximum available specific activity of the methyl donor (S-adenosyl-L-methionine, 50 mCi/mmol) would yield only 25 pCi/ml of plasma assayed. This is equivalent to 50 dpm-or less than the background of most scintillation counters.
recommended to simplify the use of the CDAL1 In two therapeutic trials in Crohn’s disease we have found that a simple index without a diary card or weighting factors is satisfactory.2,3 To compare the St Mark’s index and the CDAI we have collected data on 69 outpatient attendances of patients with Crohn’s disease. The data enable us to derive the Bristol index for our patients, and the Spearman rank correlation coefficients were r=0.79(p<0.001) for CDAI and the Brisfor CDAI and the St Mark’s tol index and r=0.83 (p<0.001)
index. It is not surprising that the correlations between the simple indices and the CDAI are so good because in these data 87% of the Bristol score, 54% of the St Mark’s score, and 73% of the CDAI were contributed by three symptoms (well-being, frequency of liquid stools, and abdominal pain). The Bristol index is the simplest because it contains no laboratory data, whereas the St Mark’s index contains measurements of hxmoglobin, erythrocyte sedimentation rate, and serum albumin, which contribute little to the final score. Since our findings agree with those of the Bristol workers we propose that their simple clinical index, based solely on symptoms and signs, should be adopted as a measure of Crohn’s disease activity in the outpatient department and in the ward. This clinical index takes no account of laboratory measures of inflammation or of nutritional deficits except in so far as these affect a patient’s sense of well-being. We therefore suggest that the clinical index should be supplemented by measurements of one or more acute phase reactants and by an assessment of nutritional state.
In practice, neither the methylation nor recovery is likely to be more than 50%, and in some cases much less. Since most of the radiometric assays for catecholamines limit themselves to 50-100 lil samples (largely, doubtless, because of the high cost of the isotope), the amount of adrenaline present in the sample to be assayed is likely to be in the femtomole range. In my experience, only the recent introduction of high specific activity 3H-S-adenosyl-L-methionine (50-85 Ci/mmol) has permitted the accurate determination of adrenaline in all
St Mark’s Hospital, London EC1V 2PS
P. R. ELLIOTT J. E. LENNARD-JONES
Department of Medical Computing, St Bartholomew’s Hospital, London
N. HATHWAY
plasma sarijoles.
SIR,-The Prader-Willi syndrome is characterised by hyperphagia and gross obesity, together with neonatal hypotonia, hypogonadism, stunted stature, and low intelligence. Because of the obesity, there is a high risk of early death in cardiorespiratory failure.4 Margules et al. have shown that genetically obese and hyperphagic mice (ob/ob) and rats (fa/fa) have high levels of apparent p-endorphin immunoreactivity in the pitui-
Department of Clinical Pharmacology, Royal Postgraduate Medical School, London W12
M. J. BROWN
SIMPLE INDEX OF CROHN’S DISEASE ACTIVITY
SIR,-We congratulate Dr Harvey and Dr Bradshaw p. 514) for showing that a simple index correlates well with the more complex American Crohn’s disease activity index (CDAI). Our experience has also led us to doubt if it is necessary for a patient to complete a diary card during the week before an outpatient visit and for the doctor to calculate seven weighted criteria before adding eight values to give the index. The use of a pocket programmable calculator has been
(March 8,
so
1. Da Prada M, Zurcher G. Simultaneous radioenzymatic determination of plasma and tissue adrenaline, noradrenaline and dopamine within the femtomole range. Life Sci 1976; 19: 1151-74. 2. Peuler JD, Johnson GA. Simultaneous single isotope radioenzymatic assay of plasma norepinephrine, epinephrine and dopamine. Life Sci 1977; 21: 625-36. 3. Weise VK, Kopin IJ. Assay of catecholamines in human plasma: studies of a single isotope radioenzymatic procedure. Life Sci 1976; 19: 1673-86. 4. Hjemdahl -P, Daleskog M, Kahan T. Determination of plasma catecholamines by high performance liquid chromatography with electrochemical detection: comparison with a radioenzymatic method. Life Sci 1979; 25: 131-38. 5. Yui Y, Fujita T, Yamamoto T, et al. Liquid chromatographic determination of norepinephrine and epinephrine in human plasma. Clin Chem 1980; 26(2): 194-96. 6. Johnson GA, Peuler JD, Baker CA. Plasma catecholamines in normotensive Ther Res 1977; 21: 898-903. subjects.
Curr
EFFECT OF NALOXONE ON HYPERPHAGIA IN PRADER-WILLI SYNDROME
tary, and that treatment with a low dose of naloxone controlled the hyperphagia in these animals. Since naloxone seems free from serious side-effects, we decided on a small pilot study in Prader-Willi syndrome to assess the effect of naloxone on the abnormal eating behaviour, to see if the hyperphagia in this condition was related to an underlying abnormality in
p-endorphin activity. Three patients with Prader-Willi syndrome were studied; all were short and very obese with body mass indices (weight in kg divided by the square of height in cm multiplied by 100) were 0.342, 0.386, and 0.528 (normal <0.250). The patients attended for measurement of food intake during an 8 h period from 0930 to 1730. The amount of food consumed during each 8 h period was measured continuously with an automated food dispenser6 to which the patients had free
1. Best WR, Becktel JM. Singleton JW. Rederived values of eight coefficients of the Crohn’s disease activity index. Gastroenterology 1979; 77: 843-46. 2. Burnham WR, Lennard-Jones JE, Hecketsweiler P, Colin R, Geffroy Y. Oral BCG vaccine in Crohn’s disease. Gut 1979; 20: 229-33. 3. O’Donoghue DP, Dawson AM, Powell-Tuck J, Bown RL, Lennard-Jones JE. Double-blind withdrawal trial of azathioprine as maintenance treatment for Crohn’s disease. Lancet 1978; ii: 955-57. 4. Laurance BM, Brito A, Wilkinson J. The Prader-Willi syndrome after the age of 15 years. Arch Dis Child (in press). 5. Margules DL, Moisset B, Lewis MJ, Shibuya H, Pert CB. &bgr;-endorphin is associated with overeating in genetically obese mice (ob/ob) and rats (fa/fa).
Science 1978; 202: 988-91. 6. Silverstone T, Fincham J, Brydon J. A measurement of food intake in man. Am
technique for the J Clin Nutr (in press).
new
continuous
SIR,-Dr Mendelsohn and his colleagues (March 1, p. 492) cite their failure to find an increase in plasma catecholamines as evidence against stimulation by aagiotensin of the sympathetic nervous system. As they admit, there has been considerable controversy over the role of sympathetic activity in the genesis of essential hypertension. All the more important, then, that such studies should employ reliable and credible catecholamine assays. Mendelsohn’s values for both adrenaline and noradrenaline (double isotope method) are several times higher than values reported by those using the more sensitive single isotope assays,’-3 which in turn accord with values found by the entirely different methodology of high-performance liquid chromatography and electrochemical detection.4,5 (The presentation by Mendelsohn et al. of noradrenaline values in "pg/ml" was presumably a misprint for "ng/ml".) The method used by Mendelsohn et al. was initially used in the diagnosis of phaeochromocytoma, where circulating levels of catecholamines may be several times higher than normal. Where this is not the case, it is impossible, using a 14C-methyl donor (as is necessary in the double isotope assay used) to detect circulating adrenaline -in most individuals. Even if the 0-3pmol of adrenaline per ml of "average" plasma6were completely methylated and the ’4C-metanephrine so formed recovered 100%, the maximum available specific activity of the methyl donor (S-adenosyl-L-methionine, 50 mCi/mmol) would yield only 25 pCi/ml of plasma assayed. This is equivalent to 50 dpm-or less than the background of most scintillation counters.
recommended to simplify the use of the CDAL1 In two therapeutic trials in Crohn’s disease we have found that a simple index without a diary card or weighting factors is satisfactory.2,3 To compare the St Mark’s index and the CDAI we have collected data on 69 outpatient attendances of patients with Crohn’s disease. The data enable us to derive the Bristol index for our patients, and the Spearman rank correlation coefficients were r=0.79(p<0.001) for CDAI and the Brisfor CDAI and the St Mark’s tol index and r=0.83 (p<0.001)
index. It is not surprising that the correlations between the simple indices and the CDAI are so good because in these data 87% of the Bristol score, 54% of the St Mark’s score, and 73% of the CDAI were contributed by three symptoms (well-being, frequency of liquid stools, and abdominal pain). The Bristol index is the simplest because it contains no laboratory data, whereas the St Mark’s index contains measurements of hxmoglobin, erythrocyte sedimentation rate, and serum albumin, which contribute little to the final score. Since our findings agree with those of the Bristol workers we propose that their simple clinical index, based solely on symptoms and signs, should be adopted as a measure of Crohn’s disease activity in the outpatient department and in the ward. This clinical index takes no account of laboratory measures of inflammation or of nutritional deficits except in so far as these affect a patient’s sense of well-being. We therefore suggest that the clinical index should be supplemented by measurements of one or more acute phase reactants and by an assessment of nutritional state.
In practice, neither the methylation nor recovery is likely to be more than 50%, and in some cases much less. Since most of the radiometric assays for catecholamines limit themselves to 50-100 lil samples (largely, doubtless, because of the high cost of the isotope), the amount of adrenaline present in the sample to be assayed is likely to be in the femtomole range. In my experience, only the recent introduction of high specific activity 3H-S-adenosyl-L-methionine (50-85 Ci/mmol) has permitted the accurate determination of adrenaline in all
St Mark’s Hospital, London EC1V 2PS
P. R. ELLIOTT J. E. LENNARD-JONES
Department of Medical Computing, St Bartholomew’s Hospital, London
N. HATHWAY
plasma sarijoles.
SIR,-The Prader-Willi syndrome is characterised by hyperphagia and gross obesity, together with neonatal hypotonia, hypogonadism, stunted stature, and low intelligence. Because of the obesity, there is a high risk of early death in cardiorespiratory failure.4 Margules et al. have shown that genetically obese and hyperphagic mice (ob/ob) and rats (fa/fa) have high levels of apparent p-endorphin immunoreactivity in the pitui-
Department of Clinical Pharmacology, Royal Postgraduate Medical School, London W12
M. J. BROWN
SIMPLE INDEX OF CROHN’S DISEASE ACTIVITY
SIR,-We congratulate Dr Harvey and Dr Bradshaw p. 514) for showing that a simple index correlates well with the more complex American Crohn’s disease activity index (CDAI). Our experience has also led us to doubt if it is necessary for a patient to complete a diary card during the week before an outpatient visit and for the doctor to calculate seven weighted criteria before adding eight values to give the index. The use of a pocket programmable calculator has been
(March 8,
so
1. Da Prada M, Zurcher G. Simultaneous radioenzymatic determination of plasma and tissue adrenaline, noradrenaline and dopamine within the femtomole range. Life Sci 1976; 19: 1151-74. 2. Peuler JD, Johnson GA. Simultaneous single isotope radioenzymatic assay of plasma norepinephrine, epinephrine and dopamine. Life Sci 1977; 21: 625-36. 3. Weise VK, Kopin IJ. Assay of catecholamines in human plasma: studies of a single isotope radioenzymatic procedure. Life Sci 1976; 19: 1673-86. 4. Hjemdahl -P, Daleskog M, Kahan T. Determination of plasma catecholamines by high performance liquid chromatography with electrochemical detection: comparison with a radioenzymatic method. Life Sci 1979; 25: 131-38. 5. Yui Y, Fujita T, Yamamoto T, et al. Liquid chromatographic determination of norepinephrine and epinephrine in human plasma. Clin Chem 1980; 26(2): 194-96. 6. Johnson GA, Peuler JD, Baker CA. Plasma catecholamines in normotensive Ther Res 1977; 21: 898-903. subjects.
Curr
EFFECT OF NALOXONE ON HYPERPHAGIA IN PRADER-WILLI SYNDROME
tary, and that treatment with a low dose of naloxone controlled the hyperphagia in these animals. Since naloxone seems free from serious side-effects, we decided on a small pilot study in Prader-Willi syndrome to assess the effect of naloxone on the abnormal eating behaviour, to see if the hyperphagia in this condition was related to an underlying abnormality in
p-endorphin activity. Three patients with Prader-Willi syndrome were studied; all were short and very obese with body mass indices (weight in kg divided by the square of height in cm multiplied by 100) were 0.342, 0.386, and 0.528 (normal <0.250). The patients attended for measurement of food intake during an 8 h period from 0930 to 1730. The amount of food consumed during each 8 h period was measured continuously with an automated food dispenser6 to which the patients had free
1. Best WR, Becktel JM. Singleton JW. Rederived values of eight coefficients of the Crohn’s disease activity index. Gastroenterology 1979; 77: 843-46. 2. Burnham WR, Lennard-Jones JE, Hecketsweiler P, Colin R, Geffroy Y. Oral BCG vaccine in Crohn’s disease. Gut 1979; 20: 229-33. 3. O’Donoghue DP, Dawson AM, Powell-Tuck J, Bown RL, Lennard-Jones JE. Double-blind withdrawal trial of azathioprine as maintenance treatment for Crohn’s disease. Lancet 1978; ii: 955-57. 4. Laurance BM, Brito A, Wilkinson J. The Prader-Willi syndrome after the age of 15 years. Arch Dis Child (in press). 5. Margules DL, Moisset B, Lewis MJ, Shibuya H, Pert CB. &bgr;-endorphin is associated with overeating in genetically obese mice (ob/ob) and rats (fa/fa).
Science 1978; 202: 988-91. 6. Silverstone T, Fincham J, Brydon J. A measurement of food intake in man. Am
technique for the J Clin Nutr (in press).
new
continuous