Inter-Accusport accuracy: What are the limits of agreement?

Inter-Accusport accuracy: What are the limits of agreement?
J. Gulbin 1 & J. Fell* 2 1 Australian Institute of Sport 2 Central Queensland University
INTRODUCTION: The assessment of blood lactate in endurance sports is arguably the benchmark by which training adaptations, prescribed
training intensities, performance prediction, and indications of maximal effort are based. Consequently, lactate analysis for the assessment
and monitoring of exercise performance is commonly undertaken in most sports physiology laboratories. The determination of lactate using
manual chemistry can be time consuming while many of the semi or fully automated lactate analysers are limited in their need for a controlled
laboratory environment and associated power source.
In the field, the portable and compact Accusport blood lactate analyser (ACC) (Boehringer Mannheim) is frequently used. One distinct advantage
of a hand held analyser such as the ACC is that it enables access to lactate responses in the field enabling immediate adjustments to training
intensities. Prompt determination of lactate levels facilitates communication between athletes, coaches and physiologists and enhances the
desired outcomes of training and testing regimes.
A number of studies have evaluated the performance of the ACC in comparison with laboratory analysers (Clough et al., 1997; Fell et al., 1998;
Pinnington & Dawson, 2001; Wigglesworth et al., 1996). Generally the results of these investigations have been favourable and encourage the
use of the ACC as a training and testing instrument (Fell et al., 1998; Wigglesworth et al., 1996). Pinnington and Dawson (2001) recommend
that although association between analysers may be acceptable, specifically generated regression equations are needed when comparing
values from the ACC and other analysers
One issue yet to be resolved pertains to the limits of agreement between one ACC and another. It is not uncommon for coaches and sports
scientists to have access to multiple analysers, but is there quality control over the manufacturing and production of ACC so that all ACC and
their measurements may be used interchangeably? Similarly, when lactate results are required for research publication and comparison, does
it matter which ACC was used during the data collection?
Wigglesworth et al. (1996) used intra-class correlation coefficients to compare two ACC. Reliability coefficients ranged from r=0.80 to 0.97
within the physiological range of 1-15mM. However, while this may indicate a good degree of association between analysers it fails to establish
the limits of agreement between different ACC. If the limits of agreement between different ACC’s were inconsistent then it may be necessary
to develop a separate regression equation required for each individual ACC, or at least use the same ACC each time when repeated testing
occurs.
STATEMENT OF THE PROBLEM: The purpose of this investigation was to determine the limits of agreement and establish the 95% confidence
intervals between generic ACC analysers.
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Inter-Accusport accuracy: What are the limits of agreement?
J. Gulbin 1 & J. Fell* 2 1 Australian Institute of Sport 2 Central Queensland University
METHODS: Four ACC were compared across a physiological range of blood lactate (1.9 to 16.7mmol/L). The analysers were labelled B, C, D
and E and were verified before use according to the manufacturer’s instructions. Thirty-one blood samples were obtained from the fingers of
athletes undertaking laboratory exercise tests. Tests consisted of a series of 5 minute steady-state workloads or a 2 minute all-out effort. A
125mL heparinised capillary tube was used to collect the blood at the end of each exercise effort. A standardised drop of blood (25mL) was
then randomly applied to the reagent strips of each ACC using a calibrated pipette.
The mean lactate values recorded by each analyser were compared using a repeated measures one-way analysis of variance (ANOVA).
Technical error of measurement (TEM) and percent TEM were calculated for inter-ACC comparison. Lactate measurements were then arbitrarily
grouped into three physiological ranges of interest. These approximated steady-state exercise (

Mean
lactate
minus
selected
analyser
B, C, D or E
(mmol/L)
1.08
0.54
-0.54
-1.08
0
Inter-Accusport accuracy: What are the limits of agreement?
J. Gulbin 1 & J. Fell* 2 1 Australian Institute of Sport 2 Central Queensland University
0 5 10 15 20
Mean of lacate analysers BCDE (mmol/L)
Total mean -b Total mean-c Total mean-d Total mean-e
Print
Index
Figure 1: Bland & Altman (1986) plot
demonstrating Grand mean lactate
concentration (mean of all four analysers) and
the difference between this mean and any
individual ACC.
La
(mmol/L)
TEM
(%)
< 4
4.99
4 to < 9
4.23
9 to 17
3.23
Table 1: Percent technical error of
measurement (TEM) and calculated 95%
confidence interval across three blood
lactate ranges.
TEM (95% CI)
(mmol/L)
±0.41 ±0.77 ±1.19
DISCUSSION: The results obtained in this
investigation support the inter-ACC
comparison of lactate measurements. The
lack of significant differences between the analysers, the limits of agreement of ±0.54 mmol/L, and a technical error of measurement of less
Mean +
2SD
Mean
Mean -
2SD
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Inter-Accusport accuracy: What are the limits of agreement?
J. Gulbin 1 & J. Fell* 2 1 Australian Institute of Sport 2 Central Queensland University
than 5% confirm this.
Previous comparisons between different ACC have been favourable. Wigglesworth et al. (1996) reported a high degree of reliability between
ACC with intra-class correlation coefficients ranging from r=0.80 to 0.97 up to 15mM, and found no significant difference between analysers
using a repeated measures ANOVA. Supporting and extending on the findings by Wigglesworth and colleagues, the limits of agreement or
approximate 95% confidence interval (m±2SD; [0.54mmol/L]) between the multiple ACC reported in this study are well within clinically acceptable
levels for hand held analysers of this type (American Diabetes Association, 1995).
The physiological range measured in this study (1.9-16.7mmol/L) may not encompass all blood lactate concentrations elicited during rest and
supra-maximal exercise. Measured values in these upper ranges of lactate concentration should be treated with some caution. This is partly
due to evidence of heteroscedasticity (a relationship between the degree of disparity between analysers and the level of lactate measured)
above 10mmol/L (Figure 1). Similar findings at higher blood lactate concentrations have been reported by Pyne et al. (2000), Pinnington &
Dawson (2001) and Fell et al. (1998) when comparing the ACC with other instruments of lactate analysis. While the limits of agreement have
been demonstrated to be statistically acceptable throughout the most likely measured range, users should be aware that the greatest variability
between values occurs at the higher lactate concentrations.
Explaining the slight variation between analysers can be the subject of some speculation. These may be related to sample homogeneity,
sample stability, sample size, and equipment performance.
Sample homogeneity: While a 25mL blood sample is required to measure lactate using the ACC, a five-fold sample was collected in the present
study. It is not uncommon for exercise scientists to collect sufficient blood during a single draw (125mL) to analyse a number of rheological
- parameters of interest (eg. pH, HCO , glucose, lactate). Therefore, it may be possible that during a complicated or extended blood draw (up
3
to one minute), lactate concentration may change during collection as lactate continues to diffuse into the blood from the muscle cells (Bishop
& Martino, 1993). Although in the present study the samples were drawn relatively quickly by an experienced phlebotomist, sample inhomogeneity
cannot be completely discounted.
Sample stability: In this study blood samples were not treated to arrest erythrocyte glycolysis in-vitro. A mean increase in lactate in the absence
of a glycolytic inhibitor of 0.42mmol/L per hour has been shown (Astles et al., 1994). However, Williams et al. (1992) reported no mean change
Print
Index
Table of Contents
Quit

Inter-Accusport accuracy: What are the limits of agreement?
J. Gulbin 1 & J. Fell* 2 1 Australian Institute of Sport 2 Central Queensland University
in lactate concentration over 18 minutes at 20oC (24 samples). As all samples were processed within 60 seconds, it is improbable that any
latent period between the first and final application of blood to the test strip would cause lactate variability in the sample.
Sample size: While minor pipette errors during transfer from capillary tube to analyser cannot be discounted, Fell et al. (1998) have reported no
differences in the measured lactate concentrations for drop sizes between 20 and 50mL. Therefore when using a sample size of 25mL pipette
errors of up to 20% should have no impact on measured lactate concentration. Interestingly, Pyne et al., (2000) have recently discussed the
convenience of an alternative blood lactate analyser (Lactate ProTM ) which minimises the potential for experimental error via manual transfer.
‘Double handling’ of blood samples for assay using the ACC is an area that requires further investigation.
Equipment performance: Despite previously mentioned studies supporting ACC precision there remains an aspect of ambiguity in the quality
control solutions provided by the manufacturer for the assessment of instrument precision. The solutions are merely labelled high and low and
have an indicated acceptable range (low: 1.7-3.1mmol/L and high: 4.5-7.0mmol/L). In the present study, there was no known lactate concentration
used as a reference solution. Therefore, unlike other laboratory analysers there is no way of knowing whether any given ACC is measuring at,
above or below the precise concentration.
CONCLUSIONS: There is good agreement between generic ACC over the range of blood lactates of physiological interest. ACC users can be
confident that each analyser will measure each respective blood lactate measurement reliably with a technical error of measurement of less
than 5%.
ACKNOWLEDGMENTS: The authors would like to thank the assistance provided by the South Australian Sports Institute (SASI).
REFERENCES:
1. American Diabetes Association (1995). Consensus statement on self-monitoring of blood glucose. Diabetes Care 18: 46-52.
2. Astles, R., Williams, C. P. & Sedor, F. (1994). Stability of plasma lactate in vitro in the presence of antiglycolytic agents. Clinical Chemistry
40(7): 1327-1330.
3. Atkinson, G. & Neville, A. M. (1998). Statistical methods for assessing measurement error (reliability) in variables relevant to sports
medicine. Sports Medicine 26: 217-238.
4. Bishop, P. & Martino, M. (1993). Blood lactate measurement in recovery as an adjunct to training. Practical considerations. Sports
Medicine 16: 5-13.
Print
Index
Table of Contents
Quit

Inter-Accusport accuracy: What are the limits of agreement?
J. Gulbin 1 & J. Fell* 2 1 Australian Institute of Sport 2 Central Queensland University
5. Bland, J.M. & Altman, D.G. (1986). Statistical methods for assessing agreement between two methods of clinical measurement. The
Lancet Feb 8: 301-310.
6. Clough, M., Martin, D. T., Pyne, D., Kearns, A., Lee, H., Ryan, R., Ashenden, M. & Hahn, A. (1997). Interpretation of Accusport blood l
actate results - How do they compare with YSI 2300 Stat values? Australian Conference of Science and Medicine in Sport. Sports
Medicine Australia, Bruce, ACT 2616 Australia, pp 82-83.
7. Fell, J.W., Rayfield, J. M., Gulbin, J. P. & Gaffney, P. T. (1998). Evaluation of the Accusport lactate analyser. International Journal of
Sports Medicine 19: 199-204.
8. Pinnington, H. & Dawson, B. (2001). Examination of the validity and reliability of the Accusport blood lactate analyser. Journal of Science
and Medicine in Sport 4(1): 129-138.
9. Pyne, D. B., Boston, T., Martin, D. T. & Logan, A. (2000). Evaluation of the Lactate ProTM blood lactate analyser. European Journal of
Applied Physiology 82(1/2): 112-116.
10. Wigglesworth, J. K., LaMere, V. J., Rowland, N. D. & Miller, L. (1996). Examination of the reliability and validity of a new blood lactate
analyzer. Medicine and Science in Sports and Exercise 28: S10 (Abstract 59).
Williams, J. R., Armstrong, N. & Kirby, B. J. (1992). The influence of the site of sampling and assay medium upon the measurement and
interpretation of blood lactate responses to exercise. Journal of Sports Sciences 10: 95-107.
Print
Index
Table of Contents
Quit

Inter-Accusport accuracy: What are the limits of agreement?
J. Gulbin 1 & J. Fell* 2
1Australian Institute of Sport
2Central Queensland University
INTRODUCTION: The assessment of blood lactate in endurance sports is arguably the benchmark by which
training adaptations, prescribed training intensities, performance prediction, and indications of maximal effort are
based. Consequently, lactate analysis for the assessment and monitoring of exercise performance is commonly
undertaken in most sports physiology laboratories. The determination of lactate using manual chemistry can be
time consuming while many of the semi or fully automated lactate analysers are limited in their need for a
controlled laboratory environment and associated power source.
In the field, the portable and compact Accusport blood lactate analyser (ACC) (Boehringer Mannheim) is
frequently used. One distinct advantage of a hand held analyser such as the ACC is that it enables access to
lactate responses in the field enabling immediate adjustments to training intensities. Prompt determination of
lactate levels facilitates communication between athletes, coaches and physiologists and enhances the desired
outcomes of training and testing regimes.
A number of studies have evaluated the performance of the ACC in comparison with laboratory analysers
(Clough et al., 1997; Fell et al., 1998; Pinnington & Dawson, 2001; Wigglesworth et al., 1996). Generally the
results of these investigations have been favourable and encourage the use of the ACC as a training and testing
instrument (Fell et al., 1998; Wigglesworth et al., 1996). Pinnington and Dawson (2001) recommend that although
association between analysers may be acceptable, specifically generated regression equations are needed when
comparing values from the ACC and other analysers
One issue yet to be resolved pertains to the limits of agreement between one ACC and another. It is not
uncommon for coaches and sports scientists to have access to multiple analysers, but is there quality control over
the manufacturing and production of ACC so that all ACC and their measurements may be used interchangeably?
Similarly, when lactate results are required for research publication and comparison, does it matter which ACC
was used during the data collection?
Wigglesworth et al. (1996) used intra-class correlation coefficients to compare two ACC. Reliability coefficients
ranged from r=0.80 to 0.97 within the physiological range of 1-15mM. However, while this may indicate a good
degree of association between analysers it fails to establish the limits of agreement between different ACC. If the
limits of agreement between different ACC's were inconsistent then it may be necessary to develop a separate
regression equation required for each individual ACC, or at least use the same ACC each time when repeated
testing occurs.
STATEMENT OF THE PROBLEM: The purpose of this investigation was to determine the limits of agreement
and establish the 95% confidence intervals between generic ACC analysers.
METHODS: Four ACC were compared across a physiological range of blood lactate (1.9 to 16.7mmol/L). The
analysers were labelled B, C, D and E and were verified before use according to the manufacturer's instructions.
Thirty-one blood samples were obtained from the fingers of athletes undertaking laboratory exercise tests. Tests
consisted of a series of 5 minute steady-state workloads or a 2 minute all-out effort. A 125μL heparinised
capillary tube was used to collect the blood at the end of each exercise effort. A standardised drop of blood
(25μL) was then randomly applied to the reagent strips of each ACC using a calibrated pipette.
The mean lactate values recorded by each analyser were compared using a repeated measures one-way
analysis of variance (ANOVA). Technical error of measurement (TEM) and percent TEM were calculated for inter-
ACC comparison. Lactate measurements were then arbitrarily grouped into three physiological ranges of interest.
These approximated steady-state exercise (

Figure 1 is a Bland & Altman (1986) plot depicting the Grand mean lactate concentration for any single blood
sample (mean of ACC B, C, D and E) compared with the difference between the Grand mean and the value from
any individual analyser (e.g. Grand mean minus B, or C, or D, or E). The limits of agreement, or the approximate
95% confidence interval (μ±2SD) for the analyser is ±0.54 mmol/L. The technical error of measurement (TEM)
and % TEM at blood lactate concentrations of < 4 mmol/L, 4 to < 9 mmol/L, and 9 to 17 mmol/L are 0.14 (4.99%),
0.27 (4.23%) and 0.42 mmol/L (3.23%) respectively (Table 1).
Mean
lactate
minus
selected
analyser
B, C, D or E
(mmol/L)
Figure 1: Bland & Altman (1986) plot demonstrating Grand mean lactate concentration (mean of all four
analysers) and the difference between this mean and any individual ACC.
La
(mmol/L)
TEM
(%)
TEM (95% CI)
(mmol/L)
1.08
0.54
-0.54
-1.08
0
0 5 10 15 20
Mean of lacate analysers BCDE (mmol/L)
Total mean -b Total mean-c Total mean-d Total mean-e
< 4 4 to < 9 9 to 17
4.99 4.23 3.23
±0.41 ±0.77 ±1.19
Mean +
2SD
Table 1: Percent technical error of measurement (TEM) and calculated 95% confidence interval across three
blood lactate ranges.
DISCUSSION: The results obtained in this investigation support the inter-ACC comparison of lactate
measurements. The lack of significant differences between the analysers, the limits of agreement of ±0.54
mmol/L, and a technical error of measurement of less than 5% confirm this.
Previous comparisons between different ACC have been favourable. Wigglesworth et al. (1996) reported a
high degree of reliability between ACC with intra-class correlation coefficients ranging from r=0.80 to 0.97 up to
15mM, and found no significant difference between analysers using a repeated measures ANOVA. Supporting
and extending on the findings by Wigglesworth and colleagues, the limits of agreement or approximate 95%
confidence interval (μ±2SD; [0.54mmol/L]) between the multiple ACC reported in this study are well within
clinically acceptable levels for hand held analysers of this type (American Diabetes Association, 1995).
The physiological range measured in this study (1.9-16.7mmol/L) may not encompass all blood lactate
concentrations elicited during rest and supra-maximal exercise. Measured values in these upper ranges of lactate
concentration should be treated with some caution. This is partly due to evidence of heteroscedasticity (a
relationship between the degree of disparity between analysers and the level of lactate measured) above
10mmol/L (Figure 1). Similar findings at higher blood lactate concentrations have been reported by Pyne et al.
(2000), Pinnington & Dawson (2001) and Fell et al. (1998) when comparing the ACC with other instruments of
lactate analysis. While the limits of agreement have been demonstrated to be statistically acceptable throughout
the most likely measured range, users should be aware that the greatest variability between values occurs at the
higher lactate concentrations.
Explaining the slight variation between analysers can be the subject of some speculation. These may be
related to sample homogeneity, sample stability, sample size, and equipment performance.
Mean
Mean -
2SD

Sample homogeneity: While a 25μL blood sample is required to measure lactate using the ACC, a five-fold
sample was collected in the present study. It is not uncommon for exercise scientists to collect sufficient blood
during a single draw (125μL) to analyse a number of rheological parameters of interest (eg. pH, HCO3 -, glucose,
lactate). Therefore, it may be possible that during a complicated or extended blood draw (up to one minute),
lactate concentration may change during collection as lactate continues to diffuse into the blood from the muscle
cells (Bishop & Martino, 1993). Although in the present study the samples were drawn relatively quickly by an
experienced phlebotomist, sample inhomogeneity cannot be completely discounted.
Sample stability: In this study blood samples were not treated to arrest erythrocyte glycolysis in-vitro. A mean
increase in lactate in the absence of a glycolytic inhibitor of 0.42mmol/L per hour has been shown (Astles et al.,
1994). However, Williams et al. (1992) reported no mean change in lactate concentration over 18 minutes at 20 oC
(24 samples). As all samples were processed within 60 seconds, it is improbable that any latent period between
the first and final application of blood to the test strip would cause lactate variability in the sample.
Sample size: While minor pipette errors during transfer from capillary tube to analyser cannot be discounted,
Fell et al. (1998) have reported no differences in the measured lactate concentrations for drop sizes between 20
and 50μL. Therefore when using a sample size of 25μL pipette errors of up to 20% should have no impact on
measured lactate concentration. Interestingly, Pyne et al., (2000) have recently discussed the convenience of an
alternative blood lactate analyser (Lactate Pro TM) which minimises the potential for experimental error via manual
transfer. 'Double handling' of blood samples for assay using the ACC is an area that requires further
investigation.
Equipment performance: Despite previously mentioned studies supporting ACC precision there remains an
aspect of ambiguity in the quality control solutions provided by the manufacturer for the assessment of instrument
precision. The solutions are merely labelled high and low and have an indicated acceptable range (low: 1.7-
3.1mmol/L and high: 4.5-7.0mmol/L). In the present study, there was no known lactate concentration used as a
reference solution. Therefore, unlike other laboratory analysers there is no way of knowing whether any given
ACC is measuring at, above or below the precise concentration.
CONCLUSIONS: There is good agreement between generic ACC over the range of blood lactates of
physiological interest. ACC users can be confident that each analyser will measure each respective blood lactate
measurement reliably with a technical error of measurement of less than 5%.
ACKNOWLEDGMENTS: The authors would like to thank the assistance provided by the South Australian
Sports Institute (SASI).
REFERENCES:
1. American Diabetes Association (1995). Consensus statement on self-monitoring of blood glucose.
Diabetes Care 18: 46-52.
2. Astles, R., Williams, C. P. & Sedor, F. (1994). Stability of plasma lactate in vitro in the presence of
antiglycolytic agents. Clinical Chemistry 40(7): 1327-1330.
3. Atkinson, G. & Neville, A. M. (1998). Statistical methods for assessing measurement error (reliability) in
variables relevant to sports medicine. Sports Medicine 26: 217-238.
4. Bishop, P. & Martino, M. (1993). Blood lactate measurement in recovery as an adjunct to training.
Practical considerations. Sports Medicine 16: 5-13.
5. Bland, J.M. & Altman, D.G. (1986). Statistical methods for assessing agreement between two methods of
clinical measurement. The Lancet Feb 8: 301-310.
6. Clough, M., Martin, D. T., Pyne, D., Kearns, A., Lee, H., Ryan, R., Ashenden, M. & Hahn, A. (1997).
Interpretation of Accusport blood lactate results - How do they compare with YSI 2300 Stat values?
Australian Conference of Science and Medicine in Sport. Sports Medicine Australia, Bruce, ACT 2616
Australia, pp 82-83.
7. Fell, J.W., Rayfield, J. M., Gulbin, J. P. & Gaffney, P. T. (1998). Evaluation of the Accusport lactate
analyser. International Journal of Sports Medicine 19: 199-204.
8. Pinnington, H. & Dawson, B. (2001). Examination of the validity and reliability of the Accusport blood
lactate analyser. Journal of Science and Medicine in Sport 4(1): 129-138.
9. Pyne, D. B., Boston, T., Martin, D. T. & Logan, A. (2000). Evaluation of the Lactate Pro TM blood lactate
analyser. European Journal of Applied Physiology 82(1/2): 112-116.
10. Wigglesworth, J. K., LaMere, V. J., Rowland, N. D. & Miller, L. (1996). Examination of the reliability and
validity of a new blood lactate analyzer. Medicine and Science in Sports and Exercise 28: S10 (Abstract
59).

11. Williams, J. R., Armstrong, N. & Kirby, B. J. (1992). The influence of the site of sampling and assay
medium upon the measurement and interpretation of blood lactate responses to exercise. Journal of
Sports Sciences 10: 95-107.