LUMAT LB 9507 - 6. CUT-OFF Measurements; 6.1 Introduction

LB 9507 Chapter 6: CUT-OFF-Measurements
6-1
6. CUT-OFF Measurements
6.1 Introduction
The aim of CUT-OFF measurements is to divide patient samples
into 3 qualitative classes separated by 2 CUT-OFF thresholds
(LOW and HIGH CUT-OFF) using fixed parameters and controls.
The samples are marked as follows:
RLU value below LOW CUT-OFF ”NEG”
RLU value between LOW and HIGH CUT-OFF ”+/-”
RLU value above HIGH CUT-OFF “POS”
Both CUT-OFF thresholds are calculated as follows:
LOW CUT-OFF = A
L
+ B
L
·(neg. std) + C
L
(1st pos. ctrl)
HIGH CUT-OFF = A
H
+ B
H
·(neg. std) + C
H
(1st pos. ctrl)
where the following are defined in the protocol:
A
L
= LOW CUT-OFF offset (RLU) Display no. C22
A
H
= HIGH CUT-OFF offset (RLU) C25
B
L
= LOW CUT-OFF FACTOR
C23
influence of the neg. control on LOW CUT-OFF
B
H
= HIGH CUT-OFF FACTOR C26
influence of the neg. control on HIGH CUT-OFF
C
L
= LOW CUT-OFF LPOS. FACTOR C24
influence of the pos. control on LOW CUT-OFF
C
H
= HIGH CUT-OFF LPOS. FACTOR C27
influence of the pos. control on HIGH CUT-OFF
This program can be flexibly used with these parameters.
Example 1 Setting the number of controls to zero results in the CUT-OFF
thresholds being defined only from the OFFSET values.
Example 2 Setting the number of the pos. controls to zero results in the CUT-
OFF threshold being defined from the neg. control and - when
entered - from the OFFSET values.
Example 3 Setting B
H
and C
L
to zero results in the CUT-OFF thresholds being
defined only from the neg. resp. pos. controls and - when entered
- from the OFFSET values.