RVEF

1. 20140519 morning meeting 胡蓮欣
Correlation vs Agreement

2. ex: SV,
SBP
只好用間接方法測量。
這方法在最初經過證明
量得很準(或是相對最
準的)取得gold
standard的地位, ex: 血
壓計
or
如果新方法跟舊法
有很好的一致性，
則會是另一選擇，
甚至可能取代舊法
未知or不易得知
真值
間接方法測量
新方法測量
已知or很容易得知
的真值
方法A 方法B
跟真值比較
Calibration
Lancet, 1986; i: 307-310
比的是correlation &
agreement

3. Example:
探討兩種flow meter測量PEFR的結果
Lancet, 1986; i: 307-310

4. First step:
plot the data and draw the line of
equality
Lancet, 1986; i: 307-310

5. Second step is usually to calculate
the correlation coefficient (r)
r = 0.94 (p < 0.001)
因為H0 (兩種flow meter的結果不會有線性相關)成立的機
率很小 推翻H0是很安全的 H1成立
兩種flow meter的結果是線性相關的!
 但是，兩種結果的高度相關性不代表一致性好
 Perfect correlation: if the points lie along any straight
line
 Perfect agreement: only if the points in the fig 1 lie
along the line of equality
一致性好，相關性一定好; 相關性好，一致性不一定好
Lancet, 1986; i: 307-310

6. Third step: Measuring agreement
the Bland–Altman plot
Lancet, 1986; i: 307-310
Limit of
agreement : (LoA)

7. 未知or不易得知
真值
間接方法測量
新方法測
量
已知or很容易
得知的真值
方法A 方法B
RVEF
MRI
FP-RNA GBPS

8. Material and methods
 24 healthy volunteers
 Caucasians
 no Hx/symptoms of heart disease or other chronic
disease
 Mean age: 44 years (range: 25–60)
 Male 71%, female 29%
 Mean BMI 25 kg/m2 (range: 19–32)
 FP-RNA+GBPS (same day) and MRI: within 1
month

9. ~19-24 mCi

12. Results
23 22 29

13. RVEF (MRI- FP)
0.05 - 2x 0.07 = -
0.09
0.05 + 2x 0.07 = 0.19

14. RVEF (MRI- GBPS)
0.06 - 2x 0.085 = -
0.11
0.06 + 2x 0.085 =

15. RVEF (FP- GBPS)
0.01 - 2x 0.10 = -
0.19
0.01 + 2x 0.10 = 0.21

17. RVEDVI (MR-GBPS)
6 - 2x 13.5 = -21
6 + 2x 13.5 = 33

18. RVESVI (MR-GBPS)
-2 - 2x 7.5 = -17
-2 + 2x 7.5 = 13

19. RVESVI (MR-GBPS)
8 - 2x 9.75 = -12
8+ 2x 9.75 = 27

20. Systemic bias and Limit of agreement
(LoA)
左欄-右欄 MRI FP-RNA GBPS
MRI - / /
FP-RNA -0.05/wide - /
GBPS -0.06/even wider No/widest -

21. Some points I agree with
 RVEF is of interest in:
 pulmonary hypertension
 chronic pulmonary diseases enlargement
 congenital heart diseases
 The three most used modalities to assess RVEF:
 FP-RNA, GBPS, cMRI
 “2D echocardiography as we believe it is generally
not considered a quantitative method with regard to
the right ventricle”
 “Planar equilibrium multiple ECG-gated isotope
ventriculography is not useful for RVEF as it is not
possible to separate the right ventricle and its
results show a very high variability”

22. And some points that I don’t…

23. European Cardiology, 2012;8(2):108–

24. European Cardiology, 2012;8(2):108–

25. European Cardiology, 2012;8(2):108–

26. European Cardiology, 2012;8(2):108–

27. European Cardiology, 2012;8(2):108–

28. In summary
 Measurements of RVEF differ significantly
between MRI and FP or GBPS
 And, different normal limit of RVEF
 MRI: 0.49-0.72
 FP: 0.44-0.66
 GBPS: 0.40-0.69
 The LoA between the methods are wide
 Not interchangable!
不一致，但是否相關呢？
未知or不易得知
真值
間接方法測量
新方法測
量
MRI
FP-RNA GBPS
•But MRI being the gold standard of RVEF?
?

29.  Thanks for your listening.