Cochran Mantel Haenszel Test with Breslow-Day Test & Quadratic Equation

© drtamil@gmail.com 2020
Cochran-Mantel-Haenszel
FK6193
Dr Azmi Mohd Tamil

Historically
• Pearson’s Chi-Square Test (1904)
• Likelihood Ratio Test
• Cochran Test (1954)
• Mantel-Haenszel Test (1959)
• Breslow-Day Test (1980)
• Tarone (1985)

Mantel-Haenszel
• An excellent method for adjusting for
confounding factors when analysing the
relationship between a dichotomous risk
factor and a dichotomous outcome.

Example
• Those with high catecholamine are
believed to be of high risk for coronary
heart disease. However age & ECG
changes are probable confounders.
– RF - Catecholamine (Low / High)
– Outcome - CHD (Present / Absent)
– Confounders
• Age (<55, 55+)
• ECG ( +, - )

Combine All
CHD + CHD -
High Cat 27(22.1%) 95 122
Low Cat 44(9.0%) 443 487
71 538 609
Crude OR = 2.86, X2=16.25

Stratification
• To control confounding factors, we divide
the sample into a series of strata, which
are now internally homogenous with
regards to the confounding factors.
• The odds ratio calculated within each
stratum are free of bias arising from
confounding.

Age < 55, ECG -
CHD + CHD -
High Cat 1(12.5%) 7 8
Low Cat 17(6.2%) 257 274
18 264 282
OR = (1 x 257)/(7 x 17) = 2.16

Age < 55, ECG +
CHD + CHD -
High Cat 3(17.6%) 14 17
Low Cat 7(11.9%) 52 59
10 66 76
OR = (3 x 52)/(14 x 7) = 1.59

Age 55+, ECG -
CHD + CHD -
High Cat 9(23.1%) 30 39
Low Cat 15(12.3%) 107 122
24 137 161
OR = (9 x 107)/(30 x 15) = 2.14

Age 55+, ECG +
CHD + CHD -
High Cat 14(24.1%) 44 58
Low Cat 5(15.6%) 27 32
19 71 90
OR = (14 x 27)/(44 x 5) = 1.72

Odds Ratio
Stratum Risk + Risk - OR
<55, ECG+ 3(17.6%) 7(11.9%) 1.59
55+, ECG+ 14(24.1%) 5(15.6%) 1.72
55+, ECG- 9(23.1%) 15(12.3%) 2.14
<55, ECG- 1(12.5%) 17(6.2%) 2.16
Combined 27(22.1%) 44(9.0%) 2.86

CI=OR.exp+1.96√1/a+1/b+1/c+1/d
Stratum OR Lower Higher
<55, ECG+ 1.59 0.36 6.96
55+, ECG+ 1.72 0.56 5.31
55+, ECG- 2.14 0.85 5.37
<55, ECG- 2.16 0.25 18.58
Combined 2.86 1.69 4.85

Odds Ratio
Stratum OR
<55, ECG+ 1.59
55+, ECG+ 1.72
55+, ECG- 2.14
<55, ECG- 2.16
Combined 2.86
• Despite stratification, stress
constantly leads to higher odds
(but not significant) of getting
CHD.
• There seems to be little effect
modification due to age and
ECG. The odds are similar.
But combined table stronger
& highly significant
OR=2.86;1.69<OR<4.85.
• Need an adjusted summary
measure & adjust for effect of
age & ECG.

Chi-Square
Cochran-Mantel-Haenszel

Testing for Overall Association
D+ D-
E+ a b a+b
E- c d c+d
a+c b+d n

Age < 55, ECG -
CHD + CHD -
High Cat 1 7 8
Low Cat 17 257 274
18 264 282

Age < 55, ECG +
CHD + CHD -
High Cat 3 14 17
Low Cat 7 52 59
10 66 76

Age 55+, ECG -
CHD + CHD -
High Cat 9 30 39
Low Cat 15 107 122
24 137 161

Age 55+, ECG +
CHD + CHD -
High Cat 14 44 58
Low Cat 5 27 32
19 71 90

Example

Refer to Table 3.
Look at df = 1.
X2MHtest = 4.15, larger than
3.84 (p=0.05) but smaller
than 5.02 (p=0.025).
5.02>4.15>3.84
Therefore if X2MHtest=4.15,
0.025<p<0.05.

Interpretation
• There is a significant relationship between
CAT and CHD, adjusted simultaneously
for age and ECG (p < 0.05; X2
MHtest).
Important: In the numerator, sum before squaring.
Under the null hypothesis X2
MHtest ~ Chi square (1 df)

Mantel-Haenszel
Adjusted Odds Ratio

Estimating The Adjusted OR
Stratum OR Lower Higher
<55, ECG+ 1.59 0.36 6.96
55+, ECG+ 1.72 0.56 5.31
55+, ECG- 2.14 0.85 5.37
<55, ECG- 2.16 0.25 18.58
Crude OR 2.86 1.69 4.85

Mantel-Haenszel Estimator of
Common Odds Ratio
( )
( )
=
n
bc
n
ad
MHˆ

Common/Average Odds Ratio
D+ D-
E+ a b a+b
E- c d c+d
a+c b+d n

Common/Average Odds Ratio

Conf. Interval, OR=1.89, X2=4.15

Conclusion
MHtest).
• The adjusted OR is 1.89 (1.02, 3.49).
Since the CI did not include the value of 1,
therefore it is significant.
• Those who are stressed have significantly
higher 2 times risk of developing CHD
compared to those not stressed, after
adjusting for age and ECG changes.

Breslow-Day Test
Azmi Mohd Tamil

Introduction
• Breslow & Day provided a test for
assessing the homogeneity of the odds
ratios across many tables/stratum.
• Its derivation involves solving a quadratic
equation, therefore not advisable to
calculate manually.
• I used an Excel trick to bypass the need
for quadratic equation.

where Ak( ψ) and var(ak ; ψ), denote the expected number and
the asymptotic variance of exposed cases based on the MH
adjusted odds ratio ψ , respectively.
Yep, the words doesn’t make any sense at all. You will hopefully
understand it once you see the calculation in action.
Breslow & Day proposed a statistic (Equation 4.32) for testing
the null hypothesis of homogeneity of the K true odds ratios. It
sums up the squared deviations of observed and fitted values,
each standardized by its variance

Equation 4.32
Breslow-Day uses the Mantel-Haenszel Odds Ratio to generate the
expected tables. The most optimum would be to use conditional
maximum likelihood estimator but that would need computing power.

Step 1
• Calculate the Mantel-Haenszel adjusted
Odds Ratio.

Step 2
• MH OR=1.89. If for every stratum, the
expected Odds Ratio is 1.89, what is the
expected value of cell a for all tables?
• This is where you need computers to
calculate for you. Shown only for 1st table.
• 1.89 = ad/bc = A x (274-18+A)
(8-A) x (18-A)
• A = 0.8941.
Stress CHD+ CHD- Total
High 1 7 8
Low 17 257 274
Total 18 264 282
Observed Data
OR
High 0.8941 7.1059 8 1.890
Low 17.1059 256.8941 274
Total 18 264 282
Expected Data

Quadratic Equation (1st Stratum)
• ad/bc = 1.89
• 1.89 = A x (274-18+A) where
(8-A) x (18-A)
– a = A
– b = (8 – A)
– c = (18 – A)
– d = 274 – c = (274 – 18 + A)
A
Credit to Dr Ihsan Zamzuri
p102428@siswa.ukm.edu.my

Quadratic Equation
• 1.89 = A x (274-18+A)
(8-A) x (18-A)
• 1.89 = A2 + 256A
A2–26A+144
• 1.89A2 – 49.14A + 272.16 = A2 + 256A
• 1.89A2 – A2 – 49.14A – 256A + 272.16 = 0
• 0.89A2 – 305.14A + 272.16 = 0
A
Credit to Dr Ihsan Zamzuri
p102428@siswa.ukm.edu.my

Quadratic Equation Using fx-570
• 0.89A2 – 305.14A + 272.16 = 0
• y = 0.89x2 – 305.14x + 272.16
• Press Mode 3x & select EQN for equation.
• For “Unknowns”, press right to display
“degree” then select 2 for quadratic
equation.
• Enter 0.89 for a, -305.14 for b and 272.16
for c.
• Answer x1=341.959682, x2=0.89425089.
Credit to Dr Ihsan Zamzuri p102428@siswa.ukm.edu.my

We take X=0.89425 since
341.95968 is too big for Table 1
High 0.8943 7.1057 8 1.890
Low 17.1057 256.8943 274
Total 18 264 282
Credit to Dr Ihsan Zamzuri p102428@siswa.ukm.edu.my

Step 3
• For each stratum, obtain the null
hypothesis variance of the cell count.
• Var=(1/0.8943+1/7.1057+1/17.1057+1/256.8943)-1
= 0.75684.
OR
High 0.8943 7.1057 8 1.890
Low 17.1057 256.8943 274
Total 18 264 282
Expected Data

OR
High 0.8943 7.1057 8 1.890
Low 17.1057 256.8943 274
Total 18 264 282
Expected Data
Step 4
• a = observed value
• A = expected value
• (1-0.8943)2
0.75684
= 0.014762.
• Repeat for all tables.
High 1 7 8
Low 17 257 274
Total 18 264 282
Observed Data

Stratum OR OR A€ V€ Breslow
Stress CHD+ CHD- Total Stress CHD+ CHD- Total
Young High 1 7 8 2.16 High 0.8943 7.1057 8 1.890 0.8943 0.7568 0.014762
ECG- Low 17 257 274 Low 17.1057 256.8943 274
Total 18 264 282 Total 18 264 282
Young High 3 14 17 1.59 High 3.309 13.691 17 1.890 3.3090 1.8388 0.051924
ECG+ Low 7 52 59 Low 6.691 52.309 59
Total 10 66 76 Total 10 66 76
Old High 9 30 39 2.14 High 8.442 30.558 39 1.890 8.4420 4.4474 0.07001
ECG- Low 15 107 122 Low 15.558 106.442 122
Total 24 137 161 Total 24 137 161
Old High 14 44 58 1.72 High 14.284 43.716 58 1.890 14.2840 2.9276 0.02755
ECG+ Low 5 27 32 Low 4.716 27.284 32
Total 19 71 90 Total 19 71 90
TOTALS High 27 95 122 2.86 26.929 9.971 0.164
Low 44 443 487
Total 71 538 609
Observed Data Expected Data
Excel Spreadsheet

Step 5
• Sum up all the differences and check the p
value from the chi square table (df = 3,
since 4 stratum).
• χ2
BDTest = 0.164; (d.f.=3) therefore p > 0.5.
• Since the test of homogeneity is not
significant, all the OR of the stratums are
homogenous.

Refer to Table 3.
Look at df = 3.
X2BDtest = 0.164, smaller
than 2.37 (p=0.5)
0.164>2.37
Therefore if X2BDtest=0.164,
p>0.5.

Same result as SPSS

Tarone Adjustment
Should subtract Tarone correction from Breslow-Day statistic
to get better chi-square approximation.
Tarone correction =

Why Tarone?
• Tarone noted that by using the MH Odds Ratio estimator
instead of the better conditional maximum likelihood
estimator, the Breslow–Day test statistic becomes like
the conditional likelihood score test. Since the MH
estimator is inefficient, Tarone noted that the test statistic
is stochastically larger than a χ2 random variable under
the homogeneity hypothesis.
• Tarone wrote in 1985; “this paper derives the appropriate
modification of the heterogeneity score test when the
parameter of interest is estimated by an inefficient, but
consistent, estimator.”

Summary
• CMH test assumes common odds ratio  and
tests if it is 1.
• Mantel-Haenszel estimate of the odds ratio
averages numerators and denominators before
taking the ratio.
• Breslow-Day test checks if odds ratios are
indeed common using discrepancies in
(observed – expected) cell counts.
• Tarone’s adjustment claims that using MH Odds
Ratio estimator for the test of homogeneity, is
inefficient, therefore needs to be corrected. But
the formula is all Greek to me, so I give up.

In SPSS
• In this data, we are trying to see the
relationship between CAT & CHD and see
whether AGE & ECG changes are
Confounders.

Data For Exercise
https://wp.me/p4mYLF-81

Weighted Analysis

Combined Analysis

Combine

Analyse->Descriptives->Crosstab

Select CMH statistics

Odds Ratio by Stratum

Odds Ratio
Stratum OR
<55, ECG+ 1.59
55+, ECG+ 1.72
55+, ECG- 2.14
<55, ECG- 2.16
Crude OR 2.86
• There seems to be
little effect
modification due to
age and ECG. But
combined table
stronger & highly
significant.
• Need to adjust for
effect of age & ECG.

No Interaction between Age & ECG
Changes with Catecholamine Level
Since the test of homogeneity is not significant, all
the OR of the stratums are homogenous. The
changing level of Age & ECG did not change CHD
OR much.

Adjusted OR = 1.891, different than
unadjusted OR=2.86. p value is
significant, indicating OR sig. since
Confidence Interval did not include 1.

Magnitude of Confounding > 10%
• May cause an overestimate (positive
confounding) or an underestimate (negative
confounding).
• Can be quantified by computing the percentage
difference between the crude and adjusted
measures.
• If Adjusted OR = 1.891, Crude OR=2.86.
– Epid; (2.86 – 1.891)/1.891 = 51.24%
– Stats; (2.86 - 1.891)/2.86 = 33.88%
• % larger than 10%, therefore Age/ECG changes
are positive confounding factors for CAT.

X2
MH
• Even after adjusting for Age & ECG changes,
X2
CMH is 4.19, p=0.041, therefore sig association
between CAT level & CHD.

Using SPSS X2
CMH

Using Continuity Correction X2
MH
χ2
MH = {|∑[a−(a+b)(a+c)/n]|−0.5}2
——————————————
∑(a+b)(a+c)(b+d)(c+d)/(n3−n2)

When to use Continuity Correction?
• https://www.statsdirect.com/help/
meta_analysis/mh.htm
• If any cell count in any of the stratum
tables is zero, then the continuity
correction should be applied.
• χ2
MH (|∑(a−(a+b)(a+c)/n)|−0.5)2
= —————————————
∑(a+b)(a+c)(b+d)(c+d)/(n3−n2)

Using StatCalc X2
MH
=608*((27*443)-(95*44))2
(71*538*122*487)
=16.21978128
• http://web1.sph.emory.edu/activepi/Instructors/
Kevin_MSword/lesson_12boh.htm
• The Mantel-Haenszel Test in StatCalc is a
large-sample version of Fisher's Exact Test, not
the same as CMH Chi-square.

Using StatCalc X2
MH
=608*((27*443)-(95*44))2
(71*538*122*487)
=16.21978128

Conclusion
CMH).
• The adjusted OR is 1.89 (1.02, 3.49).
Since the CI did not include the value of 1,
therefore it is significant.
• Those who are stressed have significantly
higher 2 times risk of developing CHD
compared to those not stressed, after
adjusting for age and ECG changes.

References
• David G. Kleinbaum, Lawrence L. Kupper, Hal
Morgenstern. 1982. Epidemiologic Research: Principles
and Quantitative Methods. John Wiley & Sons.
(pages 325, 447-460)
• N. E. Breslow & N. E. Day. 1980. Statistical Methods In
Cancer Research Volume 1 - The Analysis Of Case-
control Studies. International Agency For Research On
Cancer, World Health Organization. (pages 136-146)
• Robert E. Tarone. 1985. On Heterogeneity Tests Based
On Efficient Scores. Biometrika, Volume 72, Issue 1,
April 1985. (pages 91–95).

Cochran Mantel Haenszel Test with Breslow-Day Test & Quadratic Equation

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