This can result in misleading conclusions about the validity of an instrument. An overview on assessing agreement with continuous. Only the agreement of continuous variables will be considered. Measuring agreement in method comparison studies j. Barnhart department of biostatistics and bioinformatics and duke clinical research institute duke university po box 17969 durham, nc 27715 huiman. The blandaltman method is the most popular method with 178 85% studies having used this method, followed by the correlation coefficient 27% and means comparison 18%. Pdf measuring agreement in method comparison studies with.
Plotting data the first step is to plot the data and draw the line of equality on which all points would lie if the two meters gave exactly the same reading every time fig 1. Assessing agreement between methods of measurement clinical. A multivariate hierarchical bayesian approach to measuring. Statistical methods used to test for agreement of medical instruments measuring continuous variables in method comparison studies. Linear regression is another misused technique in method comparison studies. Pdf we propose a methodology for evaluation of agreement between two methods of measuring a continuous variable whose variability. In both cases we are concerned with the question of interpreting the individual clinical measurement. In 1986, bland and altman first suggested their statistical method for assessing agreement between two measurements of the same clinical variable. Only the first measurement by each method is used to illustrate the comparison of methods, the second measurement being used in the study of repeatability. Presents statistical methodologies for analyzing common types of data from method comparison experiments and illustrates their applications through detailed case studies measuring agreement. Measuring agreement in method comparison studies j martin. In 2010, we searched medline, ovid, pubmed, scopus and science direct for. Assessing agreement in method comparison studies depends on two fundamentally important components.
Statistical methods used to test for agreement of medical. A more subtle problem is illustrated by the work of carr et al. Measuring agreement in method comparison studies semantic. We discuss the statistical model underlying the classical limits of agreement and extend it to the case with replicate measurements.
In particular, in medicine, new methods or devices that are cheaper, easier to use, or less invasive, are routinely developed. Measuring agreement in method comparison studies a. Statistical methods for assessing agreement between two methods of clinical measurement. Agreement between two methods of clinical measurement can be quantified using the differences between observations made using the two methods. We found 29 features suggested for reporting such studies. Models, methods, and applications features statistical evaluation of agreement between two or more methods of measurement of a variable with a primary. Statistical methods for assessing agreement between two methods of clinical measurement this paper is reproduced by kind permission of the lancet, where it first appeared as. Blandaltman method for assessing agreement in method. Whether we are considering agreement between two measurements on the same samples repeatability or two individuals using identical methodology on identical samples reproducibility or comparing two methods, appropriate procedures are described, and worked examples are shown. It is a reference for clinical chemists, ecologists, and biomedical and other scientists who deal with development and validation of measurement methods. The use of two different methods means that this is a reproducibility study, but the term method comparison is used as it clearly communicates the changing conditions. It is recommended that replicate measurements be taken by each method, but the resulting data are more cumbersome to analyze.
May 25, 2012 the blandaltman method is the most popular method with 178 85% studies having used this method, followed by the correlation coefficient 27% and means comparison 18%. For agreement between two different methods of measurement, we ask whether we can use measurements by these two methods interchangeably, i. Models, methods, and applications features statistical evaluation of agreement between two or more methods of measurement of a variable with a primary focus on continuous data. We consider the problem of agreement evaluation that arises in method comparison studies in health sciences research. Method comparison studies are clearly a topic of permanent relevance. Here the idea of agreement plays a crucial role in method comparison studies. Statistical methods for assessing agreement between two. Method comparison problems we recently brought a new instrument from same manufacturer in house correlation study for bun seemed to show good agreement next slide inspection of results and bias plot, however, showed that while results were comparable at high values, they were significantly higher with the new method at values in the. Various statistical methods have been used to test for agreement. In clinical medicine we often wish to measure quantities in the living body, such as cardiac stroke volume or blood pressure. Choudhary1 department of mathematical sciences, fo 35 university of texas at dallas richardson, tx 750830688, usa abstract we propose a methodology for evaluation of agreement between two methods of measuring a continuous.
Comparing clinical methods of measurement statistical. Any method comparison studies assessing the agreement of medical instruments or equipment. The correct approach to analyzing method agreement is discussed. Method comparison studies are studies that compare two or more ways of measurement e. Some of these methods have been shown to be inappropriate. For example, serfontein and jaroszewicz 2 compared two methods of measuring gestational age. It is identical to a tukey meandifference plot, the name by which it is known in other fields, but was popularised in medical statistics by j.
The precision of agreement depends on the precision of each method, i. Agreement between two methods of clinical measurement can be quantified using the differences between observations made using the two methods on the. Measuring agreement in method comparison studies with heteroscedastic measurements lakshika s. Measuring agreement in method comparison studies with heteroscedastic measurements article pdf available in statistics in medicine 3229 december 20 with 852 reads how we measure reads. Oct 01, 2017 method comparison studies are clearly a topic of permanent relevance. Using the blandaltman method to measure agreement with.
Pdf measuring agreement in method comparison studies. Our 1986 paper is the most cited article in the lancet and is still being cited several times a day, but our other related papers are the most cited articles in several other journals 2, 5, 6. Apr 23, 2012 measuring agreement in method comparison studies 1597 discussionpreviously, we have described the limits of agreement approach1y2 and thenonparametric variant. Clsi 20 measurement procedure comparison and bias estimation using patient samples. Assessing new methods of clinical measurement british.
Measuring agreement in method comparison studies with heteroscedastic measurements nawarathna, lakshika s choudhary, pankaj k. We obtain the differences between measurements by the two methods for each individual and calculate the mean and standard. An overview on assessing agreement with continuous measurement huiman x. A blandaltman plot difference plot in analytical chemistry or biomedicine is a method of data plotting used in analyzing the agreement between two different assays. Choudhary1 department of mathematical sciences, fo 35 university of texas at dallas richardson, tx 750830688, usa abstract we propose a methodology for evaluation of agreement between two methods of measuring a continuous variable whose variability changes with magnitude. Measuring and promoting interrater agreement of teacher and principal performance ratings.
Measuring and promoting interrater agreement of teacher. Jul 23, 2004 in comparing agreement between two methods of measurement, one would expect a random scattering of data between the upper and lower limits of agreement 2 sd. The limits of agreement loa method altman and bland 1983, bland and altman 1986 for assessing the agreement between two methods of medical measurement is widely used. We have also described a powerful method for dealing with data where the agreementvaries in a complex way across the range of. Assessment of agreement between two or more methods of measurement is of considerable importance in many areas.
Often the slope of the least squares regression line is tested against zero. The blandaltman procedure produces limits of agreement, that is prediction limits for the difference between a measurement by one method and a measurement by the other. Method comparison studies are usually analyzed by computing limits of agreement. Measuring agreement in method comparison studies with. Some of the inappropriate methods highlighted by altman and bland since the 1980s are still in use. Nawarathna department of mathematical sciences, fo 35, university of texas at dallas, richardson, tx 75083. Blandaltman method for assessing agreement in method comparison studies. A method comparison study is used to compare two measurement methods. Measuring agreement wiley series in probability and statistics. Statistical analysis of agreement in measurement comparison. Studies examining whether a method agrees with itself are assessing the testretest reliability of that method. Babies with a gestational age of 35 weeks by one method had gestations between 34 and 39.
This is equivalent to testing the correlation coefficient against zero, and the above remarks apply. Measuring agreement in method comparison studies 7. Measuring agreement in method comparison studies sage journals. Assessing agreement between methods of measurement. Agreement between two methods of clinical measurement can be quanti. It is the differences between the measurements that should be investigated. To me that question must be addressed in the context of the individual patient, a notion that underpinned the development in around 1980 of the limits of agreement method for method comparison studies. Agreement between two methods of clinical measurement can be quantified using the differences between observations made using the two methods on the same subjects. Measuring agreement wiley series in probability and. The instruments must be applicable for use in humans. The second type of study we consider is a method comparison study, in which measurements are made using two measurement methods on a sample of subjects. Pdf statistical methods used to test for agreement of. Dec 20, 20 measuring agreement in method comparison studies with heteroscedastic measurements nawarathna, lakshika s choudhary, pankaj k. In a series of articles, bland and altman 79 advocated the use of a graphical method to plot the difference scores of two measurements against the mean for each subject and argued that if the new method agrees sufficiently well with the old, the old may be replaced.
But still some papers appear that rely on correlations in some form or another. The blandaltman technique forms two limits of agreement loa from the n. The 95% limits of agreement, estimated by mean difference 1. Models, methods, and applications is a resource for statisticians and biostatisticians engaged in data analysis, consultancy, and methodological research. They described the blandaltman plot as a mechanism for displaying and describing data from studies in which one variable is measured by two different techniques. Pdf download for measuring agreement in method comparison studies. An important parameter in determining the quality of a medical instrument is agreement with a gold standard.
Practitioners, researchers, and policymakers often. Bland jm, altman dg 1999 measuring agreement in method comparison studies. There are mainly two outcomes of such method comparison studies. Haber department of biostatistics the rollins school of public. We extend the limits of agreement approach to data with repeated measurements, proposing new estimates for equal numbers of replicates by each method on each subject, for unequal numbers of replicates, and for replicated data collected in pairs, where the underlying value of the quantity being measured is changing. Agreement between two methods of clinical measurement can be quantified using the. These studies try to determine if m 2 methods of measurement of a continuous clinical variable, such as blood pressure, cholesterol level, heart rate, etc. Often, features required for adequate interpretation of the studies were absent.