This is a data handling exercise i.e. no experiment is carried out and the data is provided for
this exercise on the day.
The aim is to learn to handle QC data. Each analyte in clinical biochemistry has defined and
agreed imprecision limits, above and below which results are rejected. One way of
calculating these limits is to run a pooled sample multiple oftimes and calculating SD and
CV, to establish the limits.
a. On the day of the exercise, you are provided with data of serum urea levels that were
assayed several times in the same run, by the urease method. The mean and the range have
been calculated for you and are given.
Use this information to prepare Shewhart/Levey Jennings and cusum plots, which have
clearly marked on them, mean for the method and/or the accepted limits of imprecision(±
b. You are provided with urea levels assayed daily for
21 days, using the same (as
above) QC material from a QC program. Using this data and the limits/range from (a) plot:
1. Shewhart/Levey Jennings plots (2 plots).
ii. cusum plot.
c. You are also provided with data from 3 different laboratories on QC performance on
urea analysis using the same the method and same QC material over the same period. Plot the
performance of the 3 laboratories on the same graph paper using any of the two
Shewhart/Levey Jennings plots. Compare the weekly and overall performance of the 3
Please see ‘Assessment information’ in the subject outline for more information on the writeup.
The write-up should among others include:
a. the concept of quality control, quality assurance and its significance in clinical
b. types of QC programs in clinical biochemistry (Introduction)
c. Shewhart and cusum plots for urea QC on separate graph papers (Section A of your
practical sheet with
QC data) (Results) . . .
d. graphs/plots (on one graph paper) using data from the 3 laboratones 1.e. Laboratones
I to 3 (Section B of your practical sheet with
QC data). The student can use any of the
two Levey-Jennings/Shewhart plots covered
(Results) . . . .
e. analyses of the data/graphs from the 3 laboratories ~d d1~cuss1?n mcludmg the
observed deviations and possible causes and remedies