The Target Range

As in the case of setting the assigned value, there are a number of different approaches to defining the target range  

In this case, the target range is chosen to ensure that laboratories obtaining a satisfactory score are producing results that are fit for a particular purpose. The chosen value is therefore related directly to a fitness for purpose statement, which may be derived from a legislative requirement. 

The target range can also be set at a value that corresponds to the level of performance that the scheme organizer, and the participants in the scheme, would like laboratories to be able to achieve. This is sometimes referred to as setting the target range by perception and is equivalent to using a fitness for purpose statement. 

It is not always easy or possible to set a target range based on fitness for purpose criteria and so in some cases alternative approaches are used. 

If the analytical method used by participants in the proficiency testing round has been validated by means of a formal collaborative trial, then the repeatability and reproducibility data from the trial can be used. The repeatability standard deviation gives an estimate of the expected variation in replicate results obtained in a single laboratory over a short period of time (with each result produced by the same analyst). The reproducibility standard deviation gives an estimate of the expected variation in replicate results obtained in different laboratories (see Chapter 4, Section 4.3.3 for further explanation of these terms). 

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Warfarin Bleeding, skin necrosis Clinical signs of bleeding3 baseline CBC and platelet count CBC and platelet count every 6 months following hospital discharge baseline aPTT and INR daily INR until two consecutive INRs are within the target range then once weekly x 2 weeks, then every month... 

Measure serum TSH 6 to 8 weeks after starting or any dose change. If the TSH level is not in the target range, alter the dose by 10% to 20% increments. 

Antithyroid drugs have a delayed effect. After 2 to 4 weeks of therapy, adjust the dose if the TSH is not in the target range (0.5-2.5 milliunits/L). Once the patient is euthyroid, consider reducing the dose of antithyroid drug to avoid hypothyroidism. 

The target range for proficiency assessment, a, is then calculated from ... 

The target range for this proficiency testing scheme has been set at 0.03 %abv, based on fitness for purpose criteria. Using an assigned value (X) of 40.04 %abv... 

For each sensor the target range, see (9), can be calculated by a nonlinear equation if target and sensor Cartesian positions are known. 

Determine the hemoglobin twice a week until it has stabilized in the target range and the maintenance dose has been established. After any dose adjustment, determine the hemoglobin twice weekly for at least 2 to 6 weeks until the hemoglobin has stabilized then monitor at regular intervals. 

The target range for the aPTT ratio during treatment (therapeutic window) should be 1.5 to 2.5. 

Dose modifications Any aPTT ratio out of the target range is to be confirmed at once before drawing conclusions with respect to dose modifications, unless there is a clinical need to react immediately. 

If the confirmed aPTT ratio is above the target range, stop the infusion for 2 hours. 

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