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Marsha A Wilcox - One of the best experts on this subject based on the ideXlab platform.

  • the sib transmission disequilibrium Test is a Mantel Haenszel Test
    American Journal of Human Genetics, 1998
    Co-Authors: Nan M Laird, Deborah Blacker, Marsha A Wilcox
    Abstract:

    To the Editor:Spielman and Ewens's (1998xA sibship Test for linkage in the presence of association: the sib transmission/disequilibrium Test. Spielman, RS and Ewens, WJ. Am J Hum Genet. 1998; 62: 450–458Abstract | Full Text | Full Text PDF | PubMed | Scopus (508)See all References1998) proposed extension of the transmission/disequilibrium Test (TDT), using discordant sibships, provides a simple and elegant way to apply the TDT in instances in which parents are not available. It is easy to see that the adapted Test, called the “sib TDT” (S-TDT), is numerically equivalent to a Mantel-Haenszel Test of trend, also known as the “Mantel extension Test” (Rosner 1995xRosner, B. See all References1995).The original Mantel-Haenszel Test is used routinely in matched case-control studies, to Test for association between disease and exposure. When exposure is expressed as a quantitative risk factor with C levels, the Mantel extension Test allows the investigator to obtain a 1-df Test against the alternative of a monotone trend. For each matched set, a 2×C table classifying subjects according to disease and exposure status is formed. The statistic is determined by assigning the columns quantitative values corresponding to exposure level. The statistic also may be derived as a score Test for no association within each matched set, by use of a model for the log odds of disease, which is linear in exposure level.To obtain the S-TDT by use of the Mantel extension Test, sibship is used as the stratifying variable, and for each sibship a 2×3 table cross-classifying sibs on the basis of disease status and genotype is formed. The quantitative value of exposure that yields the S-TDT assigns to each genotype the number of putative disease-associated alleles that a sib has (i.e., 2, 1, or 0) for genotypes AA, AB, or BB.The advantages of viewing the S-TDT as a Mantel extension Test are threefold. First, the Test is already widely available on commercial software. For example, SAS currently implements the Mantel extension Test as part of its Cochran-Mantel-Haenszel procedure. This version of the Test allows user-specified scores for the levels of the quantitative variable but does not provide a continuity correction. Another program, StatXact, provides an exact P value for the Mantel extension Test, as well as the asymptotic P value.Second, it immediately is obvious how to use the Test with other genetic models. For example, for an arbitrary genetic model, an investigator may want to use the 2-df Mantel-Haenszel Test, which makes no assumption about how risk varies with number of A alleles. To Test a dominant model, a value of 1 would be assigned to genotype AA or AB and a value of 0 to genotype BB; to Test a recessive model, exposure values of 1 for AA and of 0 for all other genotypes would be used.Third, if the marker is actually a candidate gene, the investigator may wish to estimate risk ratios. Collapsing over sibships and estimating risk ratios by use of the 2×3 margin results in biased estimates, which may be confounded because sibships may come from different populations with different disease risks and allele distributions. Instead, to estimate risk ratios, a Mantel-Haenszel estimate of odds ratio—or, in the general case, conditional logistic regression (Breslow and Day 1980xBreslow, NE and Day, NE. See all References1980)—should be used.

  • The Sib Transmission/Disequilibrium Test is a Mantel-Haenszel Test
    American Journal of Human Genetics, 1998
    Co-Authors: Nan M Laird, Deborah Blacker, Marsha A Wilcox
    Abstract:

    To the Editor:Spielman and Ewens's (1998xA sibship Test for linkage in the presence of association: the sib transmission/disequilibrium Test. Spielman, RS and Ewens, WJ. Am J Hum Genet. 1998; 62: 450–458Abstract | Full Text | Full Text PDF | PubMed | Scopus (508)See all References1998) proposed extension of the transmission/disequilibrium Test (TDT), using discordant sibships, provides a simple and elegant way to apply the TDT in instances in which parents are not available. It is easy to see that the adapted Test, called the “sib TDT” (S-TDT), is numerically equivalent to a Mantel-Haenszel Test of trend, also known as the “Mantel extension Test” (Rosner 1995xRosner, B. See all References1995).The original Mantel-Haenszel Test is used routinely in matched case-control studies, to Test for association between disease and exposure. When exposure is expressed as a quantitative risk factor with C levels, the Mantel extension Test allows the investigator to obtain a 1-df Test against the alternative of a monotone trend. For each matched set, a 2×C table classifying subjects according to disease and exposure status is formed. The statistic is determined by assigning the columns quantitative values corresponding to exposure level. The statistic also may be derived as a score Test for no association within each matched set, by use of a model for the log odds of disease, which is linear in exposure level.To obtain the S-TDT by use of the Mantel extension Test, sibship is used as the stratifying variable, and for each sibship a 2×3 table cross-classifying sibs on the basis of disease status and genotype is formed. The quantitative value of exposure that yields the S-TDT assigns to each genotype the number of putative disease-associated alleles that a sib has (i.e., 2, 1, or 0) for genotypes AA, AB, or BB.The advantages of viewing the S-TDT as a Mantel extension Test are threefold. First, the Test is already widely available on commercial software. For example, SAS currently implements the Mantel extension Test as part of its Cochran-Mantel-Haenszel procedure. This version of the Test allows user-specified scores for the levels of the quantitative variable but does not provide a continuity correction. Another program, StatXact, provides an exact P value for the Mantel extension Test, as well as the asymptotic P value.Second, it immediately is obvious how to use the Test with other genetic models. For example, for an arbitrary genetic model, an investigator may want to use the 2-df Mantel-Haenszel Test, which makes no assumption about how risk varies with number of A alleles. To Test a dominant model, a value of 1 would be assigned to genotype AA or AB and a value of 0 to genotype BB; to Test a recessive model, exposure values of 1 for AA and of 0 for all other genotypes would be used.Third, if the marker is actually a candidate gene, the investigator may wish to estimate risk ratios. Collapsing over sibships and estimating risk ratios by use of the 2×3 margin results in biased estimates, which may be confounded because sibships may come from different populations with different disease risks and allele distributions. Instead, to estimate risk ratios, a Mantel-Haenszel estimate of odds ratio—or, in the general case, conditional logistic regression (Breslow and Day 1980xBreslow, NE and Day, NE. See all References1980)—should be used.

Kennedy R Lees - One of the best experts on this subject based on the ideXlab platform.

  • influence of age on outcome from thrombolysis in acute stroke a controlled comparison in patients from the virtual international stroke trials archive vista
    Stroke, 2010
    Co-Authors: Nishant K Mishra, Patrick D Lyden, Hanschristoph Diener, Erich Bluhmki, Kennedy R Lees
    Abstract:

    Background and Purpose—Thrombolysis for acute ischemic stroke in patients aged >80 years is not approved in some countries due to limited trial data in the very elderly. We compared outcomes between thrombolysed and nonthrombolysed (control) patients from neuroprotection trials to assess any influence of age on response. Method—Among patients with ischemic stroke of known age, pretreatment severity (baseline National Institutes of Health Scale Score), and 90-day outcome (modified Rankin Scale score; National Institutes of Health Scale score), we compared the distribution of modified Rankin score in thrombolysed patients with control subjects by Cochran-Mantel-Haenszel Test and then logistic regression after adjustment for age and baseline National Institutes of Health Scale score. We examined patients ≤80 and ≥81 years separately and then each age decile. Results—Rankin data were available for 5817 patients, 1585 thrombolysed and 4232 control subjects; 20.5% were aged >80 years (mean±SD, 85.1±3.4 years). ...

  • thrombolysis is associated with consistent functional improvement across baseline stroke severity a comparison of outcomes in patients from the virtual international stroke trials archive vista
    Stroke, 2010
    Co-Authors: Nishant K Mishra, Patrick D Lyden, James C Grotta, Kennedy R Lees
    Abstract:

    Background and Purpose—Baseline stroke severity predicts outcomes among thrombolysed patients. The baseline National Institutes of Health Stroke Scale (NIHSS) thresholds are sometimes used to select patients for thrombolysis, clinical trial enrollment, or both. Using data lodged with Virtual International Stroke Trials Archive, we compared adjusted outcomes between thrombolysed and nonthrombolysed patients enrolled in neuroprotection trials (1998–2007) to assess the influence of various levels of baseline NIHSS. Method—We assessed the association of treatment with outcome, measured across the modified Rankin scale score distribution, in patients categorized by baseline NIHSS in increments of 4. We used an age and baseline NIHSS adjusted Cochran-Mantel-Haenszel Test followed by proportional odds logistic regression analysis. We report the Cochran-Mantel-Haenszel P values and estimated odds ratios (OR) for improved modified Rankin scale score distribution with treatment for patients within each baseline NIH...

Nan M Laird - One of the best experts on this subject based on the ideXlab platform.

  • the sib transmission disequilibrium Test is a Mantel Haenszel Test
    American Journal of Human Genetics, 1998
    Co-Authors: Nan M Laird, Deborah Blacker, Marsha A Wilcox
    Abstract:

    To the Editor:Spielman and Ewens's (1998xA sibship Test for linkage in the presence of association: the sib transmission/disequilibrium Test. Spielman, RS and Ewens, WJ. Am J Hum Genet. 1998; 62: 450–458Abstract | Full Text | Full Text PDF | PubMed | Scopus (508)See all References1998) proposed extension of the transmission/disequilibrium Test (TDT), using discordant sibships, provides a simple and elegant way to apply the TDT in instances in which parents are not available. It is easy to see that the adapted Test, called the “sib TDT” (S-TDT), is numerically equivalent to a Mantel-Haenszel Test of trend, also known as the “Mantel extension Test” (Rosner 1995xRosner, B. See all References1995).The original Mantel-Haenszel Test is used routinely in matched case-control studies, to Test for association between disease and exposure. When exposure is expressed as a quantitative risk factor with C levels, the Mantel extension Test allows the investigator to obtain a 1-df Test against the alternative of a monotone trend. For each matched set, a 2×C table classifying subjects according to disease and exposure status is formed. The statistic is determined by assigning the columns quantitative values corresponding to exposure level. The statistic also may be derived as a score Test for no association within each matched set, by use of a model for the log odds of disease, which is linear in exposure level.To obtain the S-TDT by use of the Mantel extension Test, sibship is used as the stratifying variable, and for each sibship a 2×3 table cross-classifying sibs on the basis of disease status and genotype is formed. The quantitative value of exposure that yields the S-TDT assigns to each genotype the number of putative disease-associated alleles that a sib has (i.e., 2, 1, or 0) for genotypes AA, AB, or BB.The advantages of viewing the S-TDT as a Mantel extension Test are threefold. First, the Test is already widely available on commercial software. For example, SAS currently implements the Mantel extension Test as part of its Cochran-Mantel-Haenszel procedure. This version of the Test allows user-specified scores for the levels of the quantitative variable but does not provide a continuity correction. Another program, StatXact, provides an exact P value for the Mantel extension Test, as well as the asymptotic P value.Second, it immediately is obvious how to use the Test with other genetic models. For example, for an arbitrary genetic model, an investigator may want to use the 2-df Mantel-Haenszel Test, which makes no assumption about how risk varies with number of A alleles. To Test a dominant model, a value of 1 would be assigned to genotype AA or AB and a value of 0 to genotype BB; to Test a recessive model, exposure values of 1 for AA and of 0 for all other genotypes would be used.Third, if the marker is actually a candidate gene, the investigator may wish to estimate risk ratios. Collapsing over sibships and estimating risk ratios by use of the 2×3 margin results in biased estimates, which may be confounded because sibships may come from different populations with different disease risks and allele distributions. Instead, to estimate risk ratios, a Mantel-Haenszel estimate of odds ratio—or, in the general case, conditional logistic regression (Breslow and Day 1980xBreslow, NE and Day, NE. See all References1980)—should be used.

  • The Sib Transmission/Disequilibrium Test is a Mantel-Haenszel Test
    American Journal of Human Genetics, 1998
    Co-Authors: Nan M Laird, Deborah Blacker, Marsha A Wilcox
    Abstract:

    To the Editor:Spielman and Ewens's (1998xA sibship Test for linkage in the presence of association: the sib transmission/disequilibrium Test. Spielman, RS and Ewens, WJ. Am J Hum Genet. 1998; 62: 450–458Abstract | Full Text | Full Text PDF | PubMed | Scopus (508)See all References1998) proposed extension of the transmission/disequilibrium Test (TDT), using discordant sibships, provides a simple and elegant way to apply the TDT in instances in which parents are not available. It is easy to see that the adapted Test, called the “sib TDT” (S-TDT), is numerically equivalent to a Mantel-Haenszel Test of trend, also known as the “Mantel extension Test” (Rosner 1995xRosner, B. See all References1995).The original Mantel-Haenszel Test is used routinely in matched case-control studies, to Test for association between disease and exposure. When exposure is expressed as a quantitative risk factor with C levels, the Mantel extension Test allows the investigator to obtain a 1-df Test against the alternative of a monotone trend. For each matched set, a 2×C table classifying subjects according to disease and exposure status is formed. The statistic is determined by assigning the columns quantitative values corresponding to exposure level. The statistic also may be derived as a score Test for no association within each matched set, by use of a model for the log odds of disease, which is linear in exposure level.To obtain the S-TDT by use of the Mantel extension Test, sibship is used as the stratifying variable, and for each sibship a 2×3 table cross-classifying sibs on the basis of disease status and genotype is formed. The quantitative value of exposure that yields the S-TDT assigns to each genotype the number of putative disease-associated alleles that a sib has (i.e., 2, 1, or 0) for genotypes AA, AB, or BB.The advantages of viewing the S-TDT as a Mantel extension Test are threefold. First, the Test is already widely available on commercial software. For example, SAS currently implements the Mantel extension Test as part of its Cochran-Mantel-Haenszel procedure. This version of the Test allows user-specified scores for the levels of the quantitative variable but does not provide a continuity correction. Another program, StatXact, provides an exact P value for the Mantel extension Test, as well as the asymptotic P value.Second, it immediately is obvious how to use the Test with other genetic models. For example, for an arbitrary genetic model, an investigator may want to use the 2-df Mantel-Haenszel Test, which makes no assumption about how risk varies with number of A alleles. To Test a dominant model, a value of 1 would be assigned to genotype AA or AB and a value of 0 to genotype BB; to Test a recessive model, exposure values of 1 for AA and of 0 for all other genotypes would be used.Third, if the marker is actually a candidate gene, the investigator may wish to estimate risk ratios. Collapsing over sibships and estimating risk ratios by use of the 2×3 margin results in biased estimates, which may be confounded because sibships may come from different populations with different disease risks and allele distributions. Instead, to estimate risk ratios, a Mantel-Haenszel estimate of odds ratio—or, in the general case, conditional logistic regression (Breslow and Day 1980xBreslow, NE and Day, NE. See all References1980)—should be used.

Nishant K Mishra - One of the best experts on this subject based on the ideXlab platform.

  • influence of age on outcome from thrombolysis in acute stroke a controlled comparison in patients from the virtual international stroke trials archive vista
    Stroke, 2010
    Co-Authors: Nishant K Mishra, Patrick D Lyden, Hanschristoph Diener, Erich Bluhmki, Kennedy R Lees
    Abstract:

    Background and Purpose—Thrombolysis for acute ischemic stroke in patients aged >80 years is not approved in some countries due to limited trial data in the very elderly. We compared outcomes between thrombolysed and nonthrombolysed (control) patients from neuroprotection trials to assess any influence of age on response. Method—Among patients with ischemic stroke of known age, pretreatment severity (baseline National Institutes of Health Scale Score), and 90-day outcome (modified Rankin Scale score; National Institutes of Health Scale score), we compared the distribution of modified Rankin score in thrombolysed patients with control subjects by Cochran-Mantel-Haenszel Test and then logistic regression after adjustment for age and baseline National Institutes of Health Scale score. We examined patients ≤80 and ≥81 years separately and then each age decile. Results—Rankin data were available for 5817 patients, 1585 thrombolysed and 4232 control subjects; 20.5% were aged >80 years (mean±SD, 85.1±3.4 years). ...

  • thrombolysis is associated with consistent functional improvement across baseline stroke severity a comparison of outcomes in patients from the virtual international stroke trials archive vista
    Stroke, 2010
    Co-Authors: Nishant K Mishra, Patrick D Lyden, James C Grotta, Kennedy R Lees
    Abstract:

    Background and Purpose—Baseline stroke severity predicts outcomes among thrombolysed patients. The baseline National Institutes of Health Stroke Scale (NIHSS) thresholds are sometimes used to select patients for thrombolysis, clinical trial enrollment, or both. Using data lodged with Virtual International Stroke Trials Archive, we compared adjusted outcomes between thrombolysed and nonthrombolysed patients enrolled in neuroprotection trials (1998–2007) to assess the influence of various levels of baseline NIHSS. Method—We assessed the association of treatment with outcome, measured across the modified Rankin scale score distribution, in patients categorized by baseline NIHSS in increments of 4. We used an age and baseline NIHSS adjusted Cochran-Mantel-Haenszel Test followed by proportional odds logistic regression analysis. We report the Cochran-Mantel-Haenszel P values and estimated odds ratios (OR) for improved modified Rankin scale score distribution with treatment for patients within each baseline NIH...

Deborah Blacker - One of the best experts on this subject based on the ideXlab platform.

  • the sib transmission disequilibrium Test is a Mantel Haenszel Test
    American Journal of Human Genetics, 1998
    Co-Authors: Nan M Laird, Deborah Blacker, Marsha A Wilcox
    Abstract:

    To the Editor:Spielman and Ewens's (1998xA sibship Test for linkage in the presence of association: the sib transmission/disequilibrium Test. Spielman, RS and Ewens, WJ. Am J Hum Genet. 1998; 62: 450–458Abstract | Full Text | Full Text PDF | PubMed | Scopus (508)See all References1998) proposed extension of the transmission/disequilibrium Test (TDT), using discordant sibships, provides a simple and elegant way to apply the TDT in instances in which parents are not available. It is easy to see that the adapted Test, called the “sib TDT” (S-TDT), is numerically equivalent to a Mantel-Haenszel Test of trend, also known as the “Mantel extension Test” (Rosner 1995xRosner, B. See all References1995).The original Mantel-Haenszel Test is used routinely in matched case-control studies, to Test for association between disease and exposure. When exposure is expressed as a quantitative risk factor with C levels, the Mantel extension Test allows the investigator to obtain a 1-df Test against the alternative of a monotone trend. For each matched set, a 2×C table classifying subjects according to disease and exposure status is formed. The statistic is determined by assigning the columns quantitative values corresponding to exposure level. The statistic also may be derived as a score Test for no association within each matched set, by use of a model for the log odds of disease, which is linear in exposure level.To obtain the S-TDT by use of the Mantel extension Test, sibship is used as the stratifying variable, and for each sibship a 2×3 table cross-classifying sibs on the basis of disease status and genotype is formed. The quantitative value of exposure that yields the S-TDT assigns to each genotype the number of putative disease-associated alleles that a sib has (i.e., 2, 1, or 0) for genotypes AA, AB, or BB.The advantages of viewing the S-TDT as a Mantel extension Test are threefold. First, the Test is already widely available on commercial software. For example, SAS currently implements the Mantel extension Test as part of its Cochran-Mantel-Haenszel procedure. This version of the Test allows user-specified scores for the levels of the quantitative variable but does not provide a continuity correction. Another program, StatXact, provides an exact P value for the Mantel extension Test, as well as the asymptotic P value.Second, it immediately is obvious how to use the Test with other genetic models. For example, for an arbitrary genetic model, an investigator may want to use the 2-df Mantel-Haenszel Test, which makes no assumption about how risk varies with number of A alleles. To Test a dominant model, a value of 1 would be assigned to genotype AA or AB and a value of 0 to genotype BB; to Test a recessive model, exposure values of 1 for AA and of 0 for all other genotypes would be used.Third, if the marker is actually a candidate gene, the investigator may wish to estimate risk ratios. Collapsing over sibships and estimating risk ratios by use of the 2×3 margin results in biased estimates, which may be confounded because sibships may come from different populations with different disease risks and allele distributions. Instead, to estimate risk ratios, a Mantel-Haenszel estimate of odds ratio—or, in the general case, conditional logistic regression (Breslow and Day 1980xBreslow, NE and Day, NE. See all References1980)—should be used.

  • The Sib Transmission/Disequilibrium Test is a Mantel-Haenszel Test
    American Journal of Human Genetics, 1998
    Co-Authors: Nan M Laird, Deborah Blacker, Marsha A Wilcox
    Abstract:

    To the Editor:Spielman and Ewens's (1998xA sibship Test for linkage in the presence of association: the sib transmission/disequilibrium Test. Spielman, RS and Ewens, WJ. Am J Hum Genet. 1998; 62: 450–458Abstract | Full Text | Full Text PDF | PubMed | Scopus (508)See all References1998) proposed extension of the transmission/disequilibrium Test (TDT), using discordant sibships, provides a simple and elegant way to apply the TDT in instances in which parents are not available. It is easy to see that the adapted Test, called the “sib TDT” (S-TDT), is numerically equivalent to a Mantel-Haenszel Test of trend, also known as the “Mantel extension Test” (Rosner 1995xRosner, B. See all References1995).The original Mantel-Haenszel Test is used routinely in matched case-control studies, to Test for association between disease and exposure. When exposure is expressed as a quantitative risk factor with C levels, the Mantel extension Test allows the investigator to obtain a 1-df Test against the alternative of a monotone trend. For each matched set, a 2×C table classifying subjects according to disease and exposure status is formed. The statistic is determined by assigning the columns quantitative values corresponding to exposure level. The statistic also may be derived as a score Test for no association within each matched set, by use of a model for the log odds of disease, which is linear in exposure level.To obtain the S-TDT by use of the Mantel extension Test, sibship is used as the stratifying variable, and for each sibship a 2×3 table cross-classifying sibs on the basis of disease status and genotype is formed. The quantitative value of exposure that yields the S-TDT assigns to each genotype the number of putative disease-associated alleles that a sib has (i.e., 2, 1, or 0) for genotypes AA, AB, or BB.The advantages of viewing the S-TDT as a Mantel extension Test are threefold. First, the Test is already widely available on commercial software. For example, SAS currently implements the Mantel extension Test as part of its Cochran-Mantel-Haenszel procedure. This version of the Test allows user-specified scores for the levels of the quantitative variable but does not provide a continuity correction. Another program, StatXact, provides an exact P value for the Mantel extension Test, as well as the asymptotic P value.Second, it immediately is obvious how to use the Test with other genetic models. For example, for an arbitrary genetic model, an investigator may want to use the 2-df Mantel-Haenszel Test, which makes no assumption about how risk varies with number of A alleles. To Test a dominant model, a value of 1 would be assigned to genotype AA or AB and a value of 0 to genotype BB; to Test a recessive model, exposure values of 1 for AA and of 0 for all other genotypes would be used.Third, if the marker is actually a candidate gene, the investigator may wish to estimate risk ratios. Collapsing over sibships and estimating risk ratios by use of the 2×3 margin results in biased estimates, which may be confounded because sibships may come from different populations with different disease risks and allele distributions. Instead, to estimate risk ratios, a Mantel-Haenszel estimate of odds ratio—or, in the general case, conditional logistic regression (Breslow and Day 1980xBreslow, NE and Day, NE. See all References1980)—should be used.