Criteria for assigning laboratory measurands to models for analytical performance specifications defined in the 1st EFLM Strategic Conference

Abstract

This paper, prepared by the EFLM Task and Finish Group on Allocation of laboratory tests to different models for performance specifications (TFG-DM), is dealing with criteria for allocating measurands to the different models for analytical performance specifications (APS) recognized in the 1st EFLM Strategic Conference Consensus Statement. Model 1, based on the effect of APS on clinical outcome, is the model of choice for measurands that have a central role in the decision-making of a specific disease or clinical situation and where cutoff/decision limits are established for either diagnosing, screening or monitoring. Total cholesterol, glucose, HbA 1c , serum albumin and cardiac troponins represent practical examples. Model 2 is based on components of biological variation and should be applied to measurands that do not have a central role in a specific disease or clinical situation, but where the concentration of the measurand is in a steady state. This is best achieved for measurands under strict homeostatic control in order to preserve their concentrations in the body fluid of interest, but it can also be applied to other measurands that are in a steady state in biological fluids. In this case, it is expected that the "noise" produced by the measurement procedure will not significantly alter the signal provided by the concentration of the measurand. This model especially applies to electrolytes and minerals in blood plasma (sodium, potassium, chloride, bicarbonate, calcium, magnesium, inorganic phosphate) and to creatinine, cystatin C, uric acid and total protein in plasma. Model 3, based on stateof-the-art of the measurement, should be used for all the measurands that cannot be included in models 1 or 2.

Patient posture for blood collection by venipuncture: recall for standardization after 28 years

“…The percentage variation calculated from the different postural positions was also compared with the desirable quality specifications for bias derived from biological variations 15 as provided by Ricos et al Briefly, this is best achieved for measurands under strict homeostatic control in order to preserve their concentrations in the body fluid of interest, but it can also be applied to other measurands that are in a steady state in biological fluids. In this case, it is expected that the ‘noise’ produced by the measurement procedure will not significantly alter the signal provided by the concentration of the measurand 16 . Each patient provided written consent before being enrolled in the study, which was performed in accord with the ethical standards established by the institution in which the experiments were performed and the Helsinki Declaration of 1975.…”

Progress and impact of enzyme measurement standardization

“…It is still under discussion under which APS model different measurands should be placed [41]. Since valid outcome data are generally not available, the biological variability model is applied to enzymes.…”

The use of error and uncertainty methods in the medical laboratory

“…Recently, criteria were formulated to assign measurands to appropriate models for analytical performance specifications [24]. The preferred performance specification model is based on clinical needs.…”

“…HbA 1c and cholesterol). The second model is based on (components of) biological variation and can be applied for measurands that are in steady state or can be "transformed" to a steady-state situation in biological fluids [24]. A third model is based on the state of the art and can be applied in cases where models 1 and 2 cannot be used.…”