Method  of  data  evaluation

17

The  following  example  Illustrates  this  comparison  process  (the  two  samples  to
be  compared  consist  of  three  peaks  each  (peak  1-3)):
Step  1  (raw  data  and  ratios)  Step  2  (features)  Step  3  (conclusion  matrix)

peak

raw  [pA]

norm**

1

193.9

0.242

RSD

CD

RSD

CD

2

257.6

0.322

1  on  1

5.1%

10.2%

33%

100%

3

329.6

0.412

2  on  2

4.8%

9.6%

1

214.7

0.268

3  on  3

5.2%

10.3%

2

283.6

0.355

3

365.5

0.457

Criterion

<  5%

<  14%

>  50%

Normalized  on  virtual  maximum  of  800  [pA]
Step  1:  The  extracted  heights  are  normalized  on  a  hypothetical  maximum  of
800  pA.  In  order  to  narrow  the  number  of  features,  a  pre-sorting  was  conducted: ­
  Every  peak  smaller  than  10%  of  the  maximum  was  not  considered  In
following  computations.  In  our  example  above,  all  normalized  peaks  a  larger
than  0.1,  so  they  were  all  used  to  calculate  features.
Step  2:  Creation  of  the  two  features  of  RSD  and  CD.  A  green  background  Indicates ­
  that  the  result  of  this  feature  Is  below  criterion  limits,  and  therefore  statistically ­
  similar.  If  these  features  exceed  their  criterion,  the  background  Is
coloured  In  red.  This  means  that  the  compared  peaks  of  the  samples  are  statistically ­
  dissimilar.
Step  3:  The  amount  of  features  showing  matches  are  compared  to  the  number
of  total  features  and  displayed  as  ratios.
The  first  step  of  extracting  peak  Intensities  and  normalisation  to  the  maximum
should  not  need  further  explanation.
Based  on  the  normalised  (“norm”)  peak  values  of  step  1,  for  every  peak  comparison ­
  the  RSD-  and  CD-features  are  created.  Looking  at  the  RSD  column
(step  2)  we  see  that  only  the  RSD  of  the  second  peak’s  comparison  Is  below
5  %  (green  background).  Since  this  Is  only  one  feature  out  of  three,  this  results
In  a  matching-ratio  of  33%  (step  3).  In  contrast,  for  CD,  step  2  shows  that  all
three  peak  comparisons  are  below  the  threshold  value  of  14%,  which  leads  to
a  100%  matching-ratio  In  step  3  for  CD 1 .

1  Note:  the  nature  and  usability  of  both  of  these  features  (RSD  and  CD)  and  how  to
proceed  and  handle  data  in  case  of  contradicting  results,  Is  not  part  of  this  investigation. ­
  Anyway,  in  the  following,  both  values  are  presented.