Bioequivalence and Bioavailability Forum

Hi Avinash,

not answering you question but a general comment. IMHO, the confusion in terminology (also in other bioanalytical guidelines) is probably caused by only a few analytical chemists (for ICH M10 just one?) involved.*

Accuracy is qualitative. We want that our result have small inaccuracy (which is quantitative). The ±15% (±20% at the LLOQ) ‘accuracy‘ stated in the guideline(s) is sloppy terminology. SCNR. I’m fine with 85–115% (80–120% at the LLOQ) of the true value or, if you prefer, ±15% (±20% at the LLOQ) inaccuracy. The term ‘non-accuracy’ is an invention of ICH.

The proper terms are unambiguously defined by the ‘International Union of Pure and Applied Chemistry’ (founded 1919!) in its ‘Golden Book’:

• Accuracy (p. 18)
  Closeness of the agreement between the result of a measurement and a true value of the measurand.
  Notes:
  
  1. Accuracy is a qualitative concept.
     
  2. The term precision should not be used for accuracy.

• Inaccuracy (p. 722)
  A quantitative term to describe the (lack of) accuracy of a chemical measurement process; comprises the imprecision and the bias. Inaccuracy must be viewed as a two-component quantity (vector); imprecision and bias should never be combined to give a scalar measure for chemical measurement process inaccuracy. (One or the other component may, however, be negligible under certain circumstances.) Inaccuracy should not be confused with uncertainty. Inaccuracy (imprecision, bias) is characteristic of the measurement process, whereas error and uncertainty are characteristics of a result. (The latter characteristic, of course, derives from the imprecision and bounds for bias of the chemical measurement process.)
  Note:

  The resultant bias and imprecision for the overall measurement process generally arise from several individual components, some of which act multiplicatively (e.g. sensitivity), and some of which act additively (e.g. the blank).

  
  
• Precision (p. 1173)
  The closeness of agreement between independent test results obtained by applying the experimental procedure under stipulated conditions. The smaller the random part of the experimental errors which affect the results, the more precise the procedure. A measure of precision (or imprecision) is the standard deviation.
  Comment:

  Precision is sometimes misused for accuracy. This problem will be avoided if one recognizes that precision relates only to dispersion, not to deviation from the (conventional) true value. Imprecision has been defined as ‘the standard error of the reported value.’

  
  
• Imprecision (p. 720)
  Variation of the result in a set of replicate measurements. This can be expressed, e.g. as the standard deviation or coefficient of variation (relative standard deviation). This term may have a more general meaning, e.g. if the replicates constitute a batch or involve different instruments, laboratories and analyst.

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• The fact that I have a heart does not qualify me to write a guideline for cardiology.