You're always WELCOME, Dr. Eman The example described above, as you said, is so simple to enable my students to catch the concept of CUSUM. In real practice, the CUSUMs are applied in different designs, and many of them are bidirectional (negative or positive directions). The determination of minimal values and alarm thresholds varies according to expert opinions, desired level of quality, clinical impact, no. Of samples per day, sensitivity of the instruments ... etc. I could provide you with a formula for rough estimation of minimal values and alarm thresholds
thank you so much dr. Tamer , this is simplified clear explanation of QC interpretation . and I wonder how to determine the SDI minimal value and alarm threshold in the CuSum? and how to calculate if the results are up and down from the mean ( + or - SDI ) do we calculate absolute SDI values or if only on one side of the QC result reading?
In cumulative sum (CUSUM) quality control, alarm thresholds and minimal values are determined based on the following factors: * **Desired level of quality:** The laboratory must first define the desired level of quality for the test in question. This is typically expressed as the maximum allowable error or bias. * **Variability of the test system:** The laboratory must also estimate the variability of the test system. This can be done by calculating the standard deviation of the test results over a period of time. * **Number of samples tested:** The number of samples tested per day or per batch will also affect the alarm thresholds and minimal values. Once these factors have been considered, the laboratory can use the following formulas to calculate the alarm thresholds and minimal values: **Alarm threshold:** ``` Alarm threshold = k * √(n) * SD ``` where: * k is a constant that depends on the desired level of quality * n is the number of samples tested per day or per batch * SD is the standard deviation of the test results **Minimal value:** ``` Minimal value = Alarm threshold / 2 ``` The alarm threshold is the point at which the CUSUM plot will signal that the test system is out of control. The minimal value is the point at which the CUSUM plot will signal that the test system is approaching a state of being out of control. The laboratory can adjust the alarm threshold and minimal value based on its own experience and the performance of the test system. For example, if the test system is very stable, the laboratory may choose to use a higher alarm threshold and minimal value. Conversely, if the test system is known to be variable, the laboratory may choose to use a lower alarm threshold and minimal value. By carefully selecting the alarm thresholds and minimal values, the laboratory can use CUSUM quality control to effectively monitor the performance of its test systems and ensure that they are providing accurate and reliable results to patients. Here are some examples of how alarm thresholds and minimal values are determined in practice: * **For a chemistry analyzer with a desired level of quality of ±2% and a standard deviation of 0.5%, the alarm threshold would be calculated as follows:** ``` Alarm threshold = 2 * √(20) * 0.5 Alarm threshold = 4.47 ``` * **The minimal value would then be calculated as follows:** ``` Minimal value = 4.47 / 2 Minimal value = 2.24 ``` * **For a hematology analyzer with a desired level of quality of ±5% and a standard deviation of 1.0%, the alarm threshold would be calculated as follows:** ``` Alarm threshold = 3 * √(20) * 1.0 Alarm threshold = 6.32 ``` * **The minimal value would then be calculated as follows:** ``` Minimal value = 6.32 / 2 Minimal value = 3.16 ``` These examples show how the alarm thresholds and minimal values can be adjusted based on the desired level of quality and the variability of the test system.
You're always WELCOME, Dr. Eman The example described above, as you said, is so simple to enable my students to catch the concept of CUSUM. In real practice, the CUSUMs are applied in different designs, and many of them are bidirectional (negative or positive directions). The determination of minimal values and alarm thresholds varies according to expert opinions, desired level of quality, clinical impact, no. Of samples per day, sensitivity of the instruments ... etc. I could provide you with formulas for rough estimation of minimal values and alarm thresholds
You're always WELCOME, Dr. Eman
The example described above, as you said, is so simple to enable my students to catch the concept of CUSUM. In real practice, the CUSUMs are applied in different designs, and many of them are bidirectional (negative or positive directions).
The determination of minimal values and alarm thresholds varies according to expert opinions, desired level of quality, clinical impact, no. Of samples per day, sensitivity of the instruments ... etc.
I could provide you with a formula for rough estimation of minimal values and alarm thresholds
❤❤❤
thank you so much dr. Tamer , this is simplified clear explanation of QC interpretation . and I wonder how to determine the SDI minimal value and alarm threshold in the CuSum? and how to calculate if the results are up and down from the mean ( + or - SDI ) do we calculate absolute SDI values or if only on one side of the QC result reading?
In cumulative sum (CUSUM) quality control, alarm thresholds and minimal values are determined based on the following factors:
* **Desired level of quality:** The laboratory must first define the desired level of quality for the test in question. This is typically expressed as the maximum allowable error or bias.
* **Variability of the test system:** The laboratory must also estimate the variability of the test system. This can be done by calculating the standard deviation of the test results over a period of time.
* **Number of samples tested:** The number of samples tested per day or per batch will also affect the alarm thresholds and minimal values.
Once these factors have been considered, the laboratory can use the following formulas to calculate the alarm thresholds and minimal values:
**Alarm threshold:**
```
Alarm threshold = k * √(n) * SD
```
where:
* k is a constant that depends on the desired level of quality
* n is the number of samples tested per day or per batch
* SD is the standard deviation of the test results
**Minimal value:**
```
Minimal value = Alarm threshold / 2
```
The alarm threshold is the point at which the CUSUM plot will signal that the test system is out of control. The minimal value is the point at which the CUSUM plot will signal that the test system is approaching a state of being out of control.
The laboratory can adjust the alarm threshold and minimal value based on its own experience and the performance of the test system. For example, if the test system is very stable, the laboratory may choose to use a higher alarm threshold and minimal value. Conversely, if the test system is known to be variable, the laboratory may choose to use a lower alarm threshold and minimal value.
By carefully selecting the alarm thresholds and minimal values, the laboratory can use CUSUM quality control to effectively monitor the performance of its test systems and ensure that they are providing accurate and reliable results to patients.
Here are some examples of how alarm thresholds and minimal values are determined in practice:
* **For a chemistry analyzer with a desired level of quality of ±2% and a standard deviation of 0.5%, the alarm threshold would be calculated as follows:**
```
Alarm threshold = 2 * √(20) * 0.5
Alarm threshold = 4.47
```
* **The minimal value would then be calculated as follows:**
```
Minimal value = 4.47 / 2
Minimal value = 2.24
```
* **For a hematology analyzer with a desired level of quality of ±5% and a standard deviation of 1.0%, the alarm threshold would be calculated as follows:**
```
Alarm threshold = 3 * √(20) * 1.0
Alarm threshold = 6.32
```
* **The minimal value would then be calculated as follows:**
```
Minimal value = 6.32 / 2
Minimal value = 3.16
```
These examples show how the alarm thresholds and minimal values can be adjusted based on the desired level of quality and the variability of the test system.
You're always WELCOME, Dr. Eman
The example described above, as you said, is so simple to enable my students to catch the concept of CUSUM. In real practice, the CUSUMs are applied in different designs, and many of them are bidirectional (negative or positive directions).
The determination of minimal values and alarm thresholds varies according to expert opinions, desired level of quality, clinical impact, no. Of samples per day, sensitivity of the instruments ... etc.
I could provide you with formulas for rough estimation of minimal values and alarm thresholds
@@tamer273 thank you so much, i think that the CUSUM Is better than applying WG rules for early detection of systematic errors as you said.