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Biological variation: contribution to test result variability
ABSTRACTS OF A N N U A L GENERAL MEETING INFLUENCE OF COAGULATION, TIME AND TEMPERATURE OF MEASUREMENT OF COMPLEMENT FACTORS C3, C ~ CC3d, , AND C4 BY IMMUNOELECTROPHORESIS
M. I. SINOSICH. B. TEISNER & J. G. GRUDZINSKAS Department of Obstetrics & Gynaecology, The Royal North Shore Hospital and The University o f Sydney. Sydney
The influence of time and ambient temperature o n the quantification of C3, C3c, C3d and C4 was compared in serum and EDTA plasma. C3 and C4 were measured by rocket immunoelectrophoresis (RIE) and C3 cleavage products. C3c and C3d. were analysed by crossed immunoelectrophoresis and double zone RIE respectively. Levels of C3 were similar in both serum and EDTA plasma and remained unchanged from zero time until 8 h after collection. Thereafter, a slight decrease in mean C3 levels seen at 24 h was followed by an increase at 48 h in both serum (of 33:3 and EDTA plasma (of 18""). In addition, a marked change in rocket morphology was seen in samples examined after 8 to 48 h at room temperature. By contrast. C4 level in both serum and EDTA plasma remained constant for 24 h. a slight decrease (of 8"") in mean levels being seen at 48 h. C3c was observed in all serum samples examined by crossed immunoelectrophoresis from zero time, whereas C3c was not detected until analysis decreased in both serum and EDTA plasma respectively to 83"" and 65"" at 24 h and 31",, and 22"" at 48 h. In addition a third precipitate previouhly unidentified was seen after 24 h. Mean levels of C3d were higher (1 3",) in serum than in EDTA plasma at zero time, and continued to increase with respect to time. The effect of coagulation. time and temperature on the assessment of complement activation are discussed in relation to these results. BILE DUCT AUTO-ANTIBODY AS DIAGNOSTIC TEST FOR ARTHRITIS
P. TRENCHEVSofia Pathology. Fairfield Human blood sera from 3000 patients with arthritis were tested by means of immunoHuorescence technique for bile duct auto-antibody. The latter was found positive in inflammatory arthritis (82",,), degenerative joint disease or tendovaginitis (4.5",), and SLE (0.5",,). Consequently the bile duct antibody is useful as a laboratory test for the diagnosis of inflammatory arthritis.
103
the inter-individual variation. conventional reference ranges are of little use and the assessment of previous levels of an analyte in an individual may give a better guide to possible pathology. In contrast. if the interindividual variation is smaller than the intra-individual variation. conventional reference ranges will be of more value. Knowledge of the intra-individual variation also alloms assessment of the imprecision required for analytical methods; it has been widely accepted that desirable imprecision (standard deviation) should be less than half the average intra-individual biological variation. QUANTITATIVE URINE ANALYSIS: A MATTER FOR CONCERN
C. G . FRASER, M. D. S. SHEPHARLI & 1.A. P ~ % B ~ K TIkptrr.trrrtvrr HY of' Clinical Biochenrist,:,,. Flinder-s Medicnl Cenrrc., S . .4. A number of approaches have been used to define acceptable standard\ of analytical performance: these have been applied. i n gencral. to analytes commonly assayed in plasma or serum. Quantitative analysis of urine is a small, but significant, part ofthe work ofmost laboratories but there has been little work on the definition of analytical goals for these analytes. Recently. goals for the analytical imprecision of I0 urine analytes have been derived from the state of the art achieved in a small interlaboratory survey [Puthn/ogj,, 13, 543. ( 198 I )] and from intra-individual biological variation in apparently healthy young men [C'lin. Clrwr.. 27, 569 (1981)l. In order to further the assessment of appropriate goals. clinicians at the Flinders Medical Centre were surveyed as to their requirements using an approach described previously [ J . Clin. Putlrol.. 32,893 (1979)l. The goals (SD)derived from these opinions ofclinician\ are shown below. The adoption of these goals. except for gluco\e u here the goal should be S D = 0.1 mmol I. is urged since. notwithstanding concerns over the objectivity of clinician responses. they are the most stringent yet derived and are targets for the future in that laboratories cannot, in general, currently meet these standards.
Analyte
Units
Sodium
mmol I I
Potassium
mmol I
BIOLOGICAL VARIATION: CONTRIBUTION TO TEST RESULT VARIABILITY
Urea
mmol I
C. G. FRASERDepurtment of' Clinical Biochemistry, Flinders Medical Centre. S . A .
Creatinine
mmol I
A number of analytes commonly assayed in plasma vary with a predictable rhythmical variation. In contrast, most analytes have no clearly defined rhythm but apparently have random variation about a set point for each individual. With careful experimental design, the total variance found on repeated assay of an analyte in a group of individuals can be dissected into analytical variance. intra-individual variance-the fluctuation of the set point of individuals-and inter-individual variance-the difference in set points among individuals. Such studies have been performed on a number of occasions on analytes commonly assayed in blood. and there is a single study on analytes frequently measured in urine; these studies have been performed on apparently healthy individuals. It has been shown that the set points of different individuals vary widely for some constituents but not for others. the degree of fluctuation about the set point may be different for different individuals. and the degree of fluctuation of certain individuals means that their analyte level is outside the conventional reference range. These facts must be taken into account when numerical results are interpreted. Knowledge of the intra- and inter-individual variation allows objective decisions to be made about the usefulness of conventional reference ranges. Where the intra-individual variation is smaller than
Calcium
mmol I
I
Goal (level) .4nalyte
Units
0.7 (10) 0.7 (100) 0.5 (10) 1.8 (100) 3.6 (300) 10.7 (600) 0.4 (10) 0.4 (20) 0.2 ( 5 ) 0.2 (10)
mmol I 11.7 (25) I .4 ( 5 0 ) mmol I 0.1 (3.0) 11 I (8.0) mmol 3 6 (300) I ( I 000) kg mmol I 0.7 (10) I .4 ( 5 0 ) p I IO.01 (0.15) 10.17 ( 5 . 0 )
Phosphate Urate Osmolalit)
Goal (level)
'
~
Glucose Proteins
-
IMPORTANCE OF FASTING PLASMA GLUCOSE CONCENTRATION AND OBESITY IN THE INTERPRETATION OF FASTING SERUM C-PEPTIDE VALUES
P. GARCIA-WEBB, A. BONSER& D. WHITING C/in/c.nl~ / ~ J ~ , / I ( , ~ ~ I ~ , s / ~ I , , Queen E1i:ahrtIr I1 Medical Centre, jVedluird.~W..4.
Reported reference values for fasting serum C-peptide reactivity (CPR) rarely take into account obesity or plasma glucose levels. However. fasting serum insulin increases with obesity and glucose stimulates insulin secretion. This study was designed to quantitate the effects of obesity and fasting plasma glucose levels on fasting CPR. Venous blood was taken from 928 fasting non-diabetic subjects for analysis of plasma glucose (hexokinase) and serum CPR. Serum CPR was measured by a sequential double antibody radioimmunoassay using reagents from Novo Research Laboratories. Ideal body weight (IBW) was calculated from life assurance tables. Plasma glucose and serum CPR results were log transformed prior t o statistical analysis. The study group comprised 529 females and 399 males ranging in age from 18-90 yr (mean 53.9 yr). Mean ( f2 sd range) serum CPR. plasma
M. I. SINOSICH. B. TEISNER & J. G. GRUDZINSKAS Department of Obstetrics & Gynaecology, The Royal North Shore Hospital and The University o f Sydney. Sydney
The influence of time and ambient temperature o n the quantification of C3, C3c, C3d and C4 was compared in serum and EDTA plasma. C3 and C4 were measured by rocket immunoelectrophoresis (RIE) and C3 cleavage products. C3c and C3d. were analysed by crossed immunoelectrophoresis and double zone RIE respectively. Levels of C3 were similar in both serum and EDTA plasma and remained unchanged from zero time until 8 h after collection. Thereafter, a slight decrease in mean C3 levels seen at 24 h was followed by an increase at 48 h in both serum (of 33:3 and EDTA plasma (of 18""). In addition, a marked change in rocket morphology was seen in samples examined after 8 to 48 h at room temperature. By contrast. C4 level in both serum and EDTA plasma remained constant for 24 h. a slight decrease (of 8"") in mean levels being seen at 48 h. C3c was observed in all serum samples examined by crossed immunoelectrophoresis from zero time, whereas C3c was not detected until analysis decreased in both serum and EDTA plasma respectively to 83"" and 65"" at 24 h and 31",, and 22"" at 48 h. In addition a third precipitate previouhly unidentified was seen after 24 h. Mean levels of C3d were higher (1 3",) in serum than in EDTA plasma at zero time, and continued to increase with respect to time. The effect of coagulation. time and temperature on the assessment of complement activation are discussed in relation to these results. BILE DUCT AUTO-ANTIBODY AS DIAGNOSTIC TEST FOR ARTHRITIS
P. TRENCHEVSofia Pathology. Fairfield Human blood sera from 3000 patients with arthritis were tested by means of immunoHuorescence technique for bile duct auto-antibody. The latter was found positive in inflammatory arthritis (82",,), degenerative joint disease or tendovaginitis (4.5",), and SLE (0.5",,). Consequently the bile duct antibody is useful as a laboratory test for the diagnosis of inflammatory arthritis.
103
the inter-individual variation. conventional reference ranges are of little use and the assessment of previous levels of an analyte in an individual may give a better guide to possible pathology. In contrast. if the interindividual variation is smaller than the intra-individual variation. conventional reference ranges will be of more value. Knowledge of the intra-individual variation also alloms assessment of the imprecision required for analytical methods; it has been widely accepted that desirable imprecision (standard deviation) should be less than half the average intra-individual biological variation. QUANTITATIVE URINE ANALYSIS: A MATTER FOR CONCERN
C. G . FRASER, M. D. S. SHEPHARLI & 1.A. P ~ % B ~ K TIkptrr.trrrtvrr HY of' Clinical Biochenrist,:,,. Flinder-s Medicnl Cenrrc., S . .4. A number of approaches have been used to define acceptable standard\ of analytical performance: these have been applied. i n gencral. to analytes commonly assayed in plasma or serum. Quantitative analysis of urine is a small, but significant, part ofthe work ofmost laboratories but there has been little work on the definition of analytical goals for these analytes. Recently. goals for the analytical imprecision of I0 urine analytes have been derived from the state of the art achieved in a small interlaboratory survey [Puthn/ogj,, 13, 543. ( 198 I )] and from intra-individual biological variation in apparently healthy young men [C'lin. Clrwr.. 27, 569 (1981)l. In order to further the assessment of appropriate goals. clinicians at the Flinders Medical Centre were surveyed as to their requirements using an approach described previously [ J . Clin. Putlrol.. 32,893 (1979)l. The goals (SD)derived from these opinions ofclinician\ are shown below. The adoption of these goals. except for gluco\e u here the goal should be S D = 0.1 mmol I. is urged since. notwithstanding concerns over the objectivity of clinician responses. they are the most stringent yet derived and are targets for the future in that laboratories cannot, in general, currently meet these standards.
Analyte
Units
Sodium
mmol I I
Potassium
mmol I
BIOLOGICAL VARIATION: CONTRIBUTION TO TEST RESULT VARIABILITY
Urea
mmol I
C. G. FRASERDepurtment of' Clinical Biochemistry, Flinders Medical Centre. S . A .
Creatinine
mmol I
A number of analytes commonly assayed in plasma vary with a predictable rhythmical variation. In contrast, most analytes have no clearly defined rhythm but apparently have random variation about a set point for each individual. With careful experimental design, the total variance found on repeated assay of an analyte in a group of individuals can be dissected into analytical variance. intra-individual variance-the fluctuation of the set point of individuals-and inter-individual variance-the difference in set points among individuals. Such studies have been performed on a number of occasions on analytes commonly assayed in blood. and there is a single study on analytes frequently measured in urine; these studies have been performed on apparently healthy individuals. It has been shown that the set points of different individuals vary widely for some constituents but not for others. the degree of fluctuation about the set point may be different for different individuals. and the degree of fluctuation of certain individuals means that their analyte level is outside the conventional reference range. These facts must be taken into account when numerical results are interpreted. Knowledge of the intra- and inter-individual variation allows objective decisions to be made about the usefulness of conventional reference ranges. Where the intra-individual variation is smaller than
Calcium
mmol I
I
Goal (level) .4nalyte
Units
0.7 (10) 0.7 (100) 0.5 (10) 1.8 (100) 3.6 (300) 10.7 (600) 0.4 (10) 0.4 (20) 0.2 ( 5 ) 0.2 (10)
mmol I 11.7 (25) I .4 ( 5 0 ) mmol I 0.1 (3.0) 11 I (8.0) mmol 3 6 (300) I ( I 000) kg mmol I 0.7 (10) I .4 ( 5 0 ) p I IO.01 (0.15) 10.17 ( 5 . 0 )
Phosphate Urate Osmolalit)
Goal (level)
'
~
Glucose Proteins
-
IMPORTANCE OF FASTING PLASMA GLUCOSE CONCENTRATION AND OBESITY IN THE INTERPRETATION OF FASTING SERUM C-PEPTIDE VALUES
P. GARCIA-WEBB, A. BONSER& D. WHITING C/in/c.nl~ / ~ J ~ , / I ( , ~ ~ I ~ , s / ~ I , , Queen E1i:ahrtIr I1 Medical Centre, jVedluird.~W..4.
Reported reference values for fasting serum C-peptide reactivity (CPR) rarely take into account obesity or plasma glucose levels. However. fasting serum insulin increases with obesity and glucose stimulates insulin secretion. This study was designed to quantitate the effects of obesity and fasting plasma glucose levels on fasting CPR. Venous blood was taken from 928 fasting non-diabetic subjects for analysis of plasma glucose (hexokinase) and serum CPR. Serum CPR was measured by a sequential double antibody radioimmunoassay using reagents from Novo Research Laboratories. Ideal body weight (IBW) was calculated from life assurance tables. Plasma glucose and serum CPR results were log transformed prior t o statistical analysis. The study group comprised 529 females and 399 males ranging in age from 18-90 yr (mean 53.9 yr). Mean ( f2 sd range) serum CPR. plasma