SHIFTS AND TRENDS IN QUALITY CONTROL

Effective Date: 
Sun, 07/01/2012
Reviewed: 
Tue, 01/10/2017
Policy: 

Commercial hematology control  values are determined each day that patient specimens are run.  They must fall within a set range that is established for that particular lot number.  lf the control  values fall within the  limits that have been set,  the entire group of patient tests of which the control specimen was a part may be reported. lf not,  the group of tests  must be repeated.

If the control values repeatedly fall above or below the mean,  the method  should be checked for systematic error.

The error may be:

  • Deterioration or gradual evaporation of reagent (increase in concentration)
  • Gradual  change in PH
  • Hemolysis

These errors may result in a trend which occurs when the values continue to either increase or decrease over an  interval  of six or more  consecutive days.

A shift occurs when values distribute themselves above or below the mean on six or more consecutive days,  but with no tendency toward either a consistent fall  or rise This usually occurs with  modifications of procedures,  changes In reagent concentration, change in line voltage,  etc.

Shifts and trends must be noted  and documented as to cause and correction on the quality control  log  sheets.

Key Points: 

There are examples in the attached PDF.