707
I
z
limits of the range of plasma-P.S.&bgr;G. after 24th week of normal pregnancy (constructed after logarithmic transformation of values).
Fig. 1-95% confidence
t
J
Year of Treatment
Long-term
response to
levodopa in respect
of stage of disease at
start of treatment.
provide dopa.
a more
definitive
answer to
this
problem with
levo-
Department of Neurology, Mount Sinai School of Medicine,
City University of New York, New York, N.Y. 10029, U.S.A.
MELVIN D. YAHR
PREGNANCY-SPECIFIC &bgr;1-GLYCOPROTEIN IN EARLY PREGNANCY
SiR,—The reports by Dr Grudzinskas, Dr Gordon and their
colleagues (Feb. 12, pp. 331 and 333), describing a radioimmunoassay for pregnancy-specific &bgr;.-glycoprotein (P.s.&bgr;G. or SPI) and pointing out the clinical value of P.s.&bgr;G. measurements in detecting fetal growth retardation, prompt us to comment on several points. First, the finding of a skewed distribution ofp.s.pG. in normal pregnancy, which Dr Gordon and his colleagues considered might be a characteristic of their radioimmunoassay technique, fits with our data for normal pregnancies studied by electroimmunoassay (fig. 1). Second, their observation that abnormally low concentrations of P.S.pG. were found in 70% of pregnancies with growth retardation of the fetus (birth-weight below 10th centile) accords with our study in which some 60% of cases of fetal growth retardation were associated with P.s.&bgr;G. levels below the normal range.’ Third, for the routine measurement of P.s.&bgr;G. in late 1. Towler,C. M., Home, C. H. W., Jandial, V., Campbell, D. M., MacGillivray,I.Br. J.Obstet.Gynœc.(inthepress).
Fig. 2-Sensitivity
and
appropriate
pregnancy, a radioimmunoassay method may not be the most convenient technique. In fig. 2 we illustrate the range of sensitivity and time taken for three standard assay techniques-namely, radial immunodiffusion using Behringwerke plates, electroimmunoassay ("rocket" immunoelectrophoresis), and radioimmunoassay. Maternal plasma levels of P.s.&bgr;G., other than in very early pregnancy, seem to be best measured by electroimmunoassay. This assay can be done in as little as 8 h; sample dilution, a possible source of error, is not required; expensive or complex equipment is not needed; and the electroimmunoassay is cheap even when applied to few samples. On the debit side, however, the electroimmunoassay cannot be automated, and this may not be the method of choice for large-scale work. We agree that radioimmunoassay is essential in the determination of P.s.&bgr;G. in very early pregnancy (8 weeks or less), and its use is clearly indicated in measurement of the plasma-p.s.&bgr;G. in patients with trophoblastic and non-trophoblastic tumours. Several non-trophoblastic tumours, such as those of the breast and gastrointestinal tract, may inappropriately produce P.S.&bgr;G.,2-4 and Tatarinov and Sokolov4 showed that 30% of patients with colorectal cancer had measurable quantities ofp.s.pG.(3-12 µg/1) in their peripheral blood. With a double-antibody radioimmunoassay technique based on the method of Chesworth we can readily measure P.S.&bgr;G. concentrations in the range 3-200 µg/1. Our preliminary
2. Horne, C. H. W., Reid, I.N., Milne, G. D. Lancet, 1976, ii, 279. 3. Horne, C. H. W., Reid, I. N., Towler, C. M., Milne, G. D. XXIVth Colloq. Protides biol.Fluids;p. 567. Bruges, 1976. 4.Tatarinov, Y. S., Sokolov, A. V. Int. J. Cancer1977, 19, 161. 5. Chesworth, J.M. Analyt. Biochem. (in the press).
range of techniques for determination of method is shown in parentheses.
P.S.&bgr;G.
The time
required for each
assay
708 results confirm that some non-trophoblastic tumours, such as colorectal cancers, do produce P.S.&bgr;G., the concentrations being similar to those found by Tatarinov and Sokolov.4
University Departments of Pathology and
C. H. W. HORNE C. M. TOWLER V. JANDIAL
Obstetrics and Gynæcology, University Medical Buildings, Foresterhill, Aberdeen AB9 2ZD
ASSESSING SEVERITY OF ASTHMA WITH WRIGHT PEAK-FLOW METER
Sir,-Knowles and Clarki reported that the change in clinical status of one of their asthmatic patients was mirrored by the changes in peak expiratory flow-rate (P.E.F.R.). This observation suggested that this test may be useful for assessing the severity of asthma. We have compared P.E.F.R. readings with blood-gas measurements in children with asthma. The P.E.F.R. was determined on eighty-four occasions in 69 children with asthma (39 boys and 30 girls). Their age range was 7 to 17 years with a mean of 10.7 years. A Wright peakflow meter was used. If a reading of at least 60 Vmin was not recorded with the adult meter, the psediatric meter was used. The best of three trials was recorded. The flow meters were recalibrated by pneumotachography and by the weighted spirometer method. The P.E.F.R. was expressed as a % of predicted mean for that narticular child.2At each of the eighty-four tests the arterialised 1-’c02, pH, and Po2 were also measured. Details of the methods are given elsewhere3 1 Knowles, G. K., Clark, T. J. H. Lancet, 1973, ii, 1356. 2.
Murray, A. B , Cook,
C.
D. J
Pediat.
1963, 62, 186.
Fig. 1--P.E.F.R. Normai range shown
v
as
PCO2. shaded
area.
% PEFR ’
Fig.
3-P.E.F.R.
Mean ± S.D. shown
as
vPO,.
parallel lines.
Children who had a P.E.F.R.of 40% or greater all had a Pco2 of 39 mmHg or less (fig. 1). The normal range for children is 35-41 mmHg.4 In mild asthma there is alveolar hyperventilation and the Peoz falls. As airway obstruction increases, in more severe asthma, there is alveolar hypoventilation. The Pco,. first rises to. high-normal levels, and then hypercapnia occurs. When our patients were divided into two groups, those with a P.E.F.R. above 40% and those below, there was a sigmficant association between low P.E.F.R. and high PC02 (P
I
z
limits of the range of plasma-P.S.&bgr;G. after 24th week of normal pregnancy (constructed after logarithmic transformation of values).
Fig. 1-95% confidence
t
J
Year of Treatment
Long-term
response to
levodopa in respect
of stage of disease at
start of treatment.
provide dopa.
a more
definitive
answer to
this
problem with
levo-
Department of Neurology, Mount Sinai School of Medicine,
City University of New York, New York, N.Y. 10029, U.S.A.
MELVIN D. YAHR
PREGNANCY-SPECIFIC &bgr;1-GLYCOPROTEIN IN EARLY PREGNANCY
SiR,—The reports by Dr Grudzinskas, Dr Gordon and their
colleagues (Feb. 12, pp. 331 and 333), describing a radioimmunoassay for pregnancy-specific &bgr;.-glycoprotein (P.s.&bgr;G. or SPI) and pointing out the clinical value of P.s.&bgr;G. measurements in detecting fetal growth retardation, prompt us to comment on several points. First, the finding of a skewed distribution ofp.s.pG. in normal pregnancy, which Dr Gordon and his colleagues considered might be a characteristic of their radioimmunoassay technique, fits with our data for normal pregnancies studied by electroimmunoassay (fig. 1). Second, their observation that abnormally low concentrations of P.S.pG. were found in 70% of pregnancies with growth retardation of the fetus (birth-weight below 10th centile) accords with our study in which some 60% of cases of fetal growth retardation were associated with P.s.&bgr;G. levels below the normal range.’ Third, for the routine measurement of P.s.&bgr;G. in late 1. Towler,C. M., Home, C. H. W., Jandial, V., Campbell, D. M., MacGillivray,I.Br. J.Obstet.Gynœc.(inthepress).
Fig. 2-Sensitivity
and
appropriate
pregnancy, a radioimmunoassay method may not be the most convenient technique. In fig. 2 we illustrate the range of sensitivity and time taken for three standard assay techniques-namely, radial immunodiffusion using Behringwerke plates, electroimmunoassay ("rocket" immunoelectrophoresis), and radioimmunoassay. Maternal plasma levels of P.s.&bgr;G., other than in very early pregnancy, seem to be best measured by electroimmunoassay. This assay can be done in as little as 8 h; sample dilution, a possible source of error, is not required; expensive or complex equipment is not needed; and the electroimmunoassay is cheap even when applied to few samples. On the debit side, however, the electroimmunoassay cannot be automated, and this may not be the method of choice for large-scale work. We agree that radioimmunoassay is essential in the determination of P.s.&bgr;G. in very early pregnancy (8 weeks or less), and its use is clearly indicated in measurement of the plasma-p.s.&bgr;G. in patients with trophoblastic and non-trophoblastic tumours. Several non-trophoblastic tumours, such as those of the breast and gastrointestinal tract, may inappropriately produce P.S.&bgr;G.,2-4 and Tatarinov and Sokolov4 showed that 30% of patients with colorectal cancer had measurable quantities ofp.s.pG.(3-12 µg/1) in their peripheral blood. With a double-antibody radioimmunoassay technique based on the method of Chesworth we can readily measure P.S.&bgr;G. concentrations in the range 3-200 µg/1. Our preliminary
2. Horne, C. H. W., Reid, I.N., Milne, G. D. Lancet, 1976, ii, 279. 3. Horne, C. H. W., Reid, I. N., Towler, C. M., Milne, G. D. XXIVth Colloq. Protides biol.Fluids;p. 567. Bruges, 1976. 4.Tatarinov, Y. S., Sokolov, A. V. Int. J. Cancer1977, 19, 161. 5. Chesworth, J.M. Analyt. Biochem. (in the press).
range of techniques for determination of method is shown in parentheses.
P.S.&bgr;G.
The time
required for each
assay
708 results confirm that some non-trophoblastic tumours, such as colorectal cancers, do produce P.S.&bgr;G., the concentrations being similar to those found by Tatarinov and Sokolov.4
University Departments of Pathology and
C. H. W. HORNE C. M. TOWLER V. JANDIAL
Obstetrics and Gynæcology, University Medical Buildings, Foresterhill, Aberdeen AB9 2ZD
ASSESSING SEVERITY OF ASTHMA WITH WRIGHT PEAK-FLOW METER
Sir,-Knowles and Clarki reported that the change in clinical status of one of their asthmatic patients was mirrored by the changes in peak expiratory flow-rate (P.E.F.R.). This observation suggested that this test may be useful for assessing the severity of asthma. We have compared P.E.F.R. readings with blood-gas measurements in children with asthma. The P.E.F.R. was determined on eighty-four occasions in 69 children with asthma (39 boys and 30 girls). Their age range was 7 to 17 years with a mean of 10.7 years. A Wright peakflow meter was used. If a reading of at least 60 Vmin was not recorded with the adult meter, the psediatric meter was used. The best of three trials was recorded. The flow meters were recalibrated by pneumotachography and by the weighted spirometer method. The P.E.F.R. was expressed as a % of predicted mean for that narticular child.2At each of the eighty-four tests the arterialised 1-’c02, pH, and Po2 were also measured. Details of the methods are given elsewhere3 1 Knowles, G. K., Clark, T. J. H. Lancet, 1973, ii, 1356. 2.
Murray, A. B , Cook,
C.
D. J
Pediat.
1963, 62, 186.
Fig. 1--P.E.F.R. Normai range shown
v
as
PCO2. shaded
area.
% PEFR ’
Fig.
3-P.E.F.R.
Mean ± S.D. shown
as
vPO,.
parallel lines.
Children who had a P.E.F.R.of 40% or greater all had a Pco2 of 39 mmHg or less (fig. 1). The normal range for children is 35-41 mmHg.4 In mild asthma there is alveolar hyperventilation and the Peoz falls. As airway obstruction increases, in more severe asthma, there is alveolar hypoventilation. The Pco,. first rises to. high-normal levels, and then hypercapnia occurs. When our patients were divided into two groups, those with a P.E.F.R. above 40% and those below, there was a sigmficant association between low P.E.F.R. and high PC02 (P
