Preparation of a QC Chart PDF

Preparation of a QC Chart Levey-Jennings Chart Levey-Jennings chart is used to graph successive QC values It uses standard deviations. Chart is prepared for each test separately. Decision limits of the test are calculated based on the normal limits with - and + 1, 2 and 3 SDs Levey-J...

Preparation of a QC Chart Levey-Jennings Chart Levey-Jennings chart is used to graph successive QC values It uses standard deviations. Chart is prepared for each test separately. Decision limits of the test are calculated based on the normal limits with - and + 1, 2 and 3 SDs Levey-Jennings Chart Mean and SD of the QC material (from the manufacturer) X-axis: time of run Y-axis: control value Most automated analyzers plot the charts; otherwise, it is drawn manually. Levey-Jennings Chart Ideally should have control values clustered about the mean with little variation in upward and downward direction Imprecision: large amount of scatter about the mean. Usually caused by errors in technique Inaccuracy: may see as a trend or a shift. Usually caused by change in testing process Random error: No pattern. Usually poor technique and malfunctioning of equipment Review charts at defined intervals, take necessary action, and document Errors which can be observed in LJ chart: 1. Trend It is formed by control values that either increase or decrease for six consecutive days. Main cause: Deterioration of reagents Errors which can be observed in LJ chart: 2. Shift It is formed by control values that distribute themselves on one side or either side of the mean for six consecutive days. Shift in the reference range is due to transient instrument differences. Main cause: Improper calibration of the instrument Errors which can be observed in LJ chart: 3. Outliers These are control values that are far from the main set of values These are highly deviating values. These are caused by random or systematic errors. Accuracy and Precision Westgard Rules IQC Procedure A stable control material that mimics patients sample is analyzed day by day. Individual measurements are plotted on a control chart called Levey-Jennings Chart. Analysis if the control is within standard limits is checked by Westgard rules Mean and Standard Deviation How to Make LJ Chart 1. Solve for the mean and SD 2. Compute for the ± 1, 2, and 3 SD. 3. Create the LJ chart. 4. Plot the data in the LJ chart. 5. Check for Westgard rules. How to Make LJ Chart 1. Solve for the mean and SD Run No. Sodium Results 1 160 2 175 = 1700 / 10 3 164 4 155 = 170 5 170 6 172 7 186 8 164 9 186 10 171 How to Make LJ Chart Run No. Sodium X-x̄ (X-x̄)2 1. Solve for the mean and SD Results 1 160 -10 100 2 175 5 25 3 164 -6 36 4 155 -15 225 5 170 0 0 = √942 / 10 6 172 2 4 =√94.2 7 186 16 256 = 9.705 or 9.71 8 164 -6 36 9 186 16 256 10 168 -2 4 942 How to Make LJ Chart Run No. Sodium X-x̄ (X-x̄)2 1. Solve for the mean and SD Results 1 160 -10 100 Mean= 170 2 175 5 25 SD= 9.71 3 164 -6 36 4 155 -15 225 5 170 0 0 6 172 2 4 7 186 16 256 8 164 -6 36 9 186 16 256 10 168 -2 4 942 How to Make LJ Chart 2. Compute for the ± 1, 2, and 3 SD. ±1S range: 170 + (9.71) (1) = 179.71 ±3S range: 170 - (9.71) (1) = 160.29 170 + (9.71) (3) 170 + 29.13 = 199.13 ±2S range: 170 + (9.71) (2) 170 - (9.71) (3) 170 + 19.42 = 189.42 170 - 29.13 = 140.87 170 - (9.71) (2) 170 - 19.42 = 150.58 How to Make LJ Chart 3. Create the LJ chart. 200 +3 SD 190 +2 SD 180 +1 SD SODIUM RESULTS 170 MEAN - 1 SD 160 - 2 SD 150 140 - 3 SD 130 0 2 4 6 8 10 12 RUN NUMBER  How to Make LJ Chart 4. Plot the data in the LJ chart. Run Sodium 200 +3 SD No. Results 190 1 160 +2 SD 2 175 180 +1 SD 3 164 SODIUM RESULTS 170 MEAN 4 155 - 1 SD 5 170 160 6 172 150 - 2 SD 7 186 140 - 3 SD 8 164 9 186 130 0 2 4 6 8 10 12 10 171 RUN NUMBER How to Make LJ Chart 5. Check for Westgard rules. 200 +3 SD 190 +2 SD 180 +1 SD SODIUM RESULTS 170 MEAN - 1 SD 160 - 2 SD 150 140 - 3 SD 130 0 2 4 6 8 10 12 RUN NUMBER How to Make LJ Chart 5. Check for Westgard rules. 200 +3 SD 190 +2 SD 180 +1 SD SODIUM RESULTS 170 MEAN - 1 SD 160 - 2 SD 150 140 - 3 SD 130 0 2 4 6 8 10 12 RUN NUMBER How to Make LJ Chart 5. Check for Westgard rules. 200 +3 SD 190 +2 SD 180 +1 SD SODIUM RESULTS 170 MEAN - 1 SD 160 - 2 SD 150 140 - 3 SD 130 0 2 4 6 8 10 12 RUN NUMBER How to Make LJ Chart 5. Check for Westgard rules. 200 +3 SD 190 +2 SD 180 +1 SD SODIUM RESULTS 170 MEAN - 1 SD 160 - 2 SD 150 140 - 3 SD 130 0 2 4 6 8 10 12 RUN NUMBER Shift and Trend TREND Values for the control that Main cause is Gradual change in the continue to either DETERIORATION OF analytic process increase or decrease over REAGENTS a period of 6 consecutive days SHIFT 6 or more consecutive daily Main cause is IMPROPER Abrupt change in the values that distribute CALIBRATION OF analytical process. Sudden themselves on one side of INSTRUMENT and sustained change in the mean value line, but one direction in control maintain a constant level sample values Dispersion Observed when random error or lack of precision increases; indicates instability problems Shift Trend Shift and Trend Westgard Multirule RULE EXPLANATION ERROR COMMENTS 1:2S 1 control exceeds ±2S from mean. Initiates testing of other rules. If no violation of Warning flag of possible change in other rules, run is considered in control. accuracy or precision. 1:3S 1 control exceeds ±3S from mean RANDOM REJECTION RULE 2:2S 2 consecutive controls exceeds 2S SYSTEMATIC REJECTION RULE from mean on same side R:4S 2 consecutive controls differ by 4S RANDOM REJECTION RULE 4:1S 4 consecutive controls exceeds 1S SYSTEMATIC REJECTION RULE from mean on the same side 10:x 10 consecutive controls on the SYSTEMATIC REJECTION RULE dame side of the mean Variables X-AXIS Horizontal Abscissa Independent Variable Y-AXIS Vertical Ordinate Dependent Variable HAXI VOYD