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Quality Requirements

Consolidated measurement uncertainty specifications

There are a number of different measurement uncertainty specifications: MAu, MAU, both in minimum and desirable specifications. And more recently, the scientific literature began describing u:ref, u:cal, u:Rw, and u:result. We've consolidated them all into one resource.

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Consolidated Comparison of Maximum Measurement Uncertainty Performance Specifications

Sten Westgard, MS

Updated November 15, 2024 with new u:result, u:ref, u:cal performance specifications, as well as updated MAU.
Updated January 2.2023 with Expanded Desirable and Minimum MU specs
Updated November 26, 2022 with Desirable and Minimum MAU
Created June 13, 2022

Mu Moose1000Uncertainty specifications are finally here. While measurement uncertainty (mu) has been mandated for decades, the benchmark for those measurements was equally uncertain. There was no consensus on how to calculate measurement uncertainty, and then once you did perform that calculation, how did you know if it was acceptable or unacceptable?

In the past year years, a new host of measurement uncertainty terms have emerged:

  • u:ref for uncertainty of reference.
  • u:cal for uncertainty of calibration
  • u:Rw for uncertainty of laboratory
  • u:result for the whole combination of all the u's

In the explanations that discuss these u's, it is said that u:ref is part of u:cal, and u:cal should take up about 50% of u:result. That leaves 50% of u:result is allowed to be designated for u:Rw, which is the laboratory imprecision.

Previously, papers have proposed different types of uncertainty goals. There was permissible uncertainty (pu), and you can find a table of that listed here. There was (mupu), and a few years ago, we were talking about Expanded Allowable Maximum Measurement Uncertainty (EAMMU, which for simplicity's sake, would be pronounced the same way as you pronounce, 'emu'). Actually, that's still not completely right, because these maximums are built on the minimum performance specification for imprecision, so it's more accurate to say EAMMMU. But if that is too much of a mouthful, you can resort to MAU, which is a different MAUthful altogether. And remember MAu and MAU are two different numbers. MAU is the expanded version of MAu, which means it takes two MAu to equal one MAU.

Below, we summarize the uncertainty goals. Where other goals than EFLM have been suggested, they are listed, but those are quite few.
Please note this is not a full reproduction of the EFLM measurement uncertainty specifications, for that please visit the EFLM website directly.

In our other consolidated listings of performance specifications, we include a recommended choice.

In this case, we have no recommendations for mu goals, because we don't recommend measurement uncertainty. Full stop.

The third to last column is the EFLM allowable total error specificaton - again, now based on the minimum level of quality. This is calculated such that TEa will always be larger than EAMMU. However, that assumes that TE is being calculated such that only 2-3 SDs will fit into the TEa (in other words, aiming only for 2 or 3 Sigma level of quality). As regular visitors of the website - regular readers of Westgard publications - know, that is not the current recommendation. TEa is to be used as a specification for 6 Sigma. So any CV specification deriving from the Six Sigma approach using TEa is actually smaller and more demanding than that offered by EAMMU, MAU, and MAu.

One will quickly note that the EAMMU is essentially twice the specification for CV. 50 years ago, 2 SD control limits were the predominant, if not the only, QC procedure of the time. So these latest advances are really sending us back into the past. Unfortunate to see so much effort poured into a recommendation that takes the laboratory backward, not forward, in quality.

Analytical performance specifications for combined uncertainty budget in the implementation of metrological traceability, Panteghini M. CCLM 2024; 62(8): 1497-1504.

Analyte  Milan
category 		 MINIMUM DESIRABLE
u:result u:rw u:cal u:ref u:result u:rw u:cal u:ref min CV MAU min MAU des
Albumin, serum bio var temp 1.25 0.625 0.625 0.42 1.88 0.94 0.94 0.63 1.9 3.8 2.5
Albumin, urine outcome 9 4.5 4.5 3.00 17 8.5 8.5 5.67      
Alk phos, serum bio var 2.65 1.325 1.325 0.88 3.98 1.99 1.99 1.33 4.5 9.0 6.0
ALT, serum bio var temp 4.65 2.325 2.325 1.55 6.98 3.49 3.49 2.33 8.6 17.1 11.4
Amylase, pancreatic, serum bio var temp 3.15 1.575 1.575 1.05 4.73 2.365 2.365 1.58  5.0 10.1 6.7
AST, serum bio var 4.75 2.375 2.375 1.58 7.13 3.565 3.565 2.38 6.4 12.9 8.6
Bilirubin, total, serum bio var 10.5 5.25 5.25 3.50 15.7 7.85 7.85 5.23  15.1 30.3 20.2
Calcium, total, serum bio var 0.91 0.455 0.455 0.30 1.36 0.68 0.68 0.45 1.4 2.7 1.8
Chloride serum bio var 0.49 0.245 0.245 0.16 0.74 0.37 0.37 0.25 0.8 1.5 1.0
Cholesterol, HDL, serum outcome 2.9 1.45 1.45 0.97 5.6 2.8 2.8 1.87 4.5 8.6 5.7
Cholesterol, total, serum outcome 3 1.5 1.5 1.00 7 3.5 3.5 2.33 3.9 7.8 5.2
Cholinesterase bio var 2.1 1.05 1.05 0.70 3.15 1.575 1.575 1.05      
CO2, total, serum bio var 2.1 1.05 1.05 0.70 3.15 1.575 1.575 1.05 3.0 6.0 4.0
Creatine kinase, serum bio var temp 7.25 3.625 3.625 2.42 10.9 5.45 5.45 3.63 10.6 21.1 14.1
Creatinine, serum bio var 2.2 1.1 1.1 0.73 3.3 1.65 1.65 1.10 3.3 6.6 4.4
CRP, serum SOTA 3.76 1.88 1.88 1.25 5.64 2.82 2.82 1.88 25.3 50.6 33.7
Cyclosporine, blood hybrid for drugs 11.5 5.75 5.75 3.83 17.2 8.6 8.6 5.73      
D-dimer, plasma bio var temp 10.6 5.3 5.3 3.53 15.9 7.95 7.95 5.30 18.9 37.8 25.2
Digoxin, serum hybrid for drugs 6 3 3 2.00 9 4.5 4.5 3.00      
Everolimus, blood hybrid for drugs 4.03 2.015 2.015 1.34 6.05 3.025 3.025 2.02      
Ferritin, serum SOTA temp 4.31 2.155 2.155 1.44 6.47 3.235 3.235 2.16 9.7 19.4 12.9
Folate, total, serum outcome 8 4 4 2.67 12 6 6 4.00 8.2 16.4 10.9
GGT, serum bio var 4.45 2.225 2.225 1.48 6.68 3.34 3.34 2.23 6.2 12.5 8.3
Glucose, fasting plasma outcome 2 1 1 0.67 3 1.5 1.5 1.00 3.4 6.9 4.6
HbA1c, blood outcome 3 1.5 1.5 1.00 3.7 1.85 1.85 1.23 0.9 1.8 1.2
HcG, intact, serum SOTA 4.55 2.275 2.275 1.52 6.83 3.415 3.415 2.28      
Hemoglobin, total, blood outcome 5.6 2.8 2.8 1.87 8.5 4.25 4.25 2.83 2.0 4.1 2.7
Homocysteine, plasma bio var 3.52 1.76 1.76 1.17 5.27 2.635 2.635 1.76  4.6 9.1 6.1
IgA, serum bio var 2.5 1.25 1.25 0.83 3.75 1.875 1.875 1.25  5.6 11.3  7.5
IgG, serum bio var 2.2 1.1 1.1 0.73 3.3 1.65 1.65 1.10  2.6 5.3 3.5
IgM, serum bio var 2.95 1.475 1.475 0.98 4.43 2.215 2.215 1.48  4.4 8.9  5.9
Lactate, plasma bio var 13.6 6.8 6.8 4.53 20.4 10.2 10.2 6.80      
LDH, serum bio var 2.6 1.3 1.3 0.87 3.9 1.95 1.95 1.30  3.3 6.6 4.4
Lipase, pancreatic, serum bio var temp 3.85 1.925 1.925 1.28 5.78 2.89 2.89 1.93  5.7 11.4 7.6
Magnesium, serum bio var 1.44 0.72 0.72 0.48 2.16 1.08 1.08 0.72  2.0 3.9 2.6
Parathyroid hormone, PTH, serum bio var 7.85 3.925 3.925 2.62 11.8 5.9 5.9 3.93  11.0 22.0 14.7
Phosphate, inorganic, serum bio var 3.84 1.92 1.92 1.28 5.75 2.875 2.875 1.92  5.8 11.6 7.7
Platelets, blood bio var temp 4.85 2.425 2.425 1.62 7.28 3.64 3.64 2.43      
Potassium serum bio var 1.96 0.98 0.98 0.65 2.94 1.47 1.47 0.98  2.9 5.8 3.9
Proteins, total, serum bio var 1.3 0.65 0.65 0.43 1.95 0.975 0.975 0.65  2.0 3.9 2.6
Proteins, total, urine SOTA temp 4.97 2.485 2.485 1.66 7.446 3.723 3.723 2.48      
PSA, serum bio var 3.4 1.7 1.7 1.13 5.1 2.55 2.55 1.70  5.1 10.2 6.8
Red Blood cells bio var 1.55 0.775 0.775 0.52 2.33 1.165 1.165 0.78  2.1 4.2 2.8
Sirolimus, blood hybrid for drugs 3.44 1.72 1.72 1.15 5.17 2.585 2.585 1.72      
Sodium serum bio var 0.27 0.135 0.135 0.09 0.4 0.2 0.2 0.13  0.4 0.8 0.5
T3, Free, serum bio var 2.35 1.175 1.175 0.78 3.53 1.765 1.765 1.18  3.8 7.6 5.1
T4, Free, serum bio var 2.8 1.4 1.4 0.93 4.2 2.1 2.1 1.40  3.6 7.2 4.8
Tacrolimus, immed. release, blood hybrid for drugs 8.27 4.135 4.135 2.76 12.4 6.2 6.2 4.13      
Transferrin, saturation, serum outcome 10 5 5 3.33 15 7.5 7.5 5.00  2.9 5.8 3.9
Triglycerides, serum outcome 6.1 3.05 3.05 2.03 12.4 6.2 6.2 4.13  14.8 29.5 19.7
Troponin, cardiac, serum outcome 9.4 4.7 4.7 3.13 13 6.5 6.5 4.33  9.5 19.0 12.7
TSH, serum SOTA temp 2.89 1.445 1.445 0.96 4.34 2.17 2.17 1.45 13.4 26.8 17.9
Urate, serum bio var 4.16 2.08 2.08 1.39 6.24 3.12 3.12 2.08 6.1 12.1 8.1
Urea, serum bio var 7.05 3.525 3.525 2.35 10.6 5.3 5.3 3.53 10.0 20.0 13.3
Vitamin D3, serum outcome 10 5 5 3.33 15 7.5 7.5 5.00  5.1  10.2 6.8
White Blood cells bio var 5.65 2.825 2.825 1.88 8.48 4.24 4.24 2.83  8.3 16.6 11.11


 For a more complete list of analyte EFLM MAU specifications, covering that analytes without specifications in the table above, see below:

Test or Analyte
2024 EFLM CV%
(minimum quality)
 2024 EFLM
Min MAU

2024 EFLM TEa
Des MAU
17-alpha-hydroxyprogesterone <21.2% < 42.5%  < 28.3%
25-hydroxy Vitamin D3 <5.1% < 10.2%  < 6.8%
Alpha-1 Antitrypsin <3.1% < 6.1%  < 4.1%
Actual bicarbonate <3.0% < 6.0%  < 4.0%
Adinoponectin <12.7% < 25.3%  < 16.9% 
Adrenaline <101.3% < 202.5%  < 135%
Alanine aminotransferase (ALT) <8.6% < 17.1% < 11.4%
Albumin <1.9% < 3.8% < 2.5%
Aldosterone <27.5% < 54.9% < 36.6%
Alkaline phosphatase bone isoenzyme <4.9%  < 9.9% < 6.6%
Alkaline phosphatase liver type <4.0% < 7.9% < 5.3%
Alphafetoprotein <3.4% < 6.9% < 4.6%
Amylase <5.0% < 10.1% < 6.7%
Apolipoprotein A1 <3.5% < 7.1%  < 4.7%
Apolipoprotein B <4.7% < 9.3% < 6.2% 
Aspartate aminotransferase (AST) <6.4% < 12.9% < 8.6%
Beta-2 microglobulin <3.1% < 6.1% < 4.1%
Basophils <9.3% < 18.6% < 12.4%
Bilirubin, total <15.1%  < 30.3% < 20.2%
Calcitonin <9.8% < 19.5% < 13.0%
C-Reactive Protein (CRP) <25.3% < 50.6%  < 33.7%
C-Reactive Protein (hs-CRP) <44.2% < 88.3% < 58.9%
Calcium, total  <1.4% < 2.7% < 1.8%
CA-125 <6.5% < 13.0% < 8.7%
CA 19-9 <3.2% <6.4% < 4.3%
CA 72-4 <37.7% <75.4% < 50.3%
Carbon dioxide total <3.0% <6.0% < 4.0%
CEA <5.1% <10.2% < 6.8%
Chloride <0.8% <1.5% < 1.0%
Cholesterol, total <3.9% <7.8% < 5.2%
Cholesterol, HDL  <4.3% <8.7% < 5.8%
Cholesterol, LDL <5.8% <11.6%  < 7.7%
Chromograinin A <11.1% <22.2% < 14.8%
Complement C3 <3.4% <6.9%  < 4.6%
Complement C4 <5.2% <10.4%  < 6.9%
Copper <5.6% <11.3% < 7.5%
Cortisol <12.1% <24.2% < 16.1%
Creatine kinase  <10.6% <21.1% < 14.1%
Creatinine  <3.3% <6.6% < 4.4%
Cystatin C <2.4% <4.8% < 3.2%
D-Dimer <18.9% < 37.8% < 25.2%
Eosinophils <11.3% <22.5% < 15.0%
Erythrocytes <2.1% <4.2% < 2.8%
Estradiol <11.3% <22.5% < 15.0%
Ferritin < 9.7% < 19.4% < 12.9%
Folate < 8.2% < 16.4% < 10.9%
Follicle stimulating hormone FSH <7.1% <14.3% < 9.5%  
Free kappa light chain <4.4% < 8.9% < 5.9%
Free lambda light chain <4.2% < 8.4% < 5.6%
Fructosamine <1.7% < 3.4% < 2.3%
GGT <6.2% < 12.5% < 8.3%
Glucose <3.4% < 6.9% < 4.6%
Glycated Albumin <1.0% < 2.1% < 1.4%
Haptoglobin <6.4% < 12.9% < 8.6%
HbA1c (NGSP) <0.9% < 1.8%  < 1.2%
HbA1c (IFCC) <1.2% < 2.4% < 1.6% 
Hemoglobin <2.0% <4.1% < 2.7%
Hematocrit <2.1% <4.2% < 2.8%
Homocysteine <4.6% < 9.1% < 6.1%
IgA <5.6% <11.3%  < 7.5%
IgG <2.6% <5.3%  < 3.5%
IgM <4.4% <8.9%  < 5.9%
Insulin <19.0% <38.1% < 25.4%
Iron, total <20.7% <41.4% < 27.6%
Lactate dehydrogenase (LDH) <3.3% <6.6% < 4.4%
Leukocytes <8.3% <16.6% < 11.1%
Lipase <5.7% <11.4% < 7.6%
Lipoprotein (a) <7.5% <15.0% <10.0%
Luteinising hormone (LH) <18.9% <37.8% < 25.2%
Lymphocytes <8.1% <16.2% < 10.8%
Magnesium <2.0% <3.9% < 2.6%
MCHC <0.8% <1.5% < 1.0%
MCH <0.5% <1.0% < 0.7%
MCV <0.6% <1.2% < 0.8%
MPV <1.7% <3.4% < 2.3%
Monocytes <10.0% <20.0% < 13.3%
Neutrophils <10.6% <21.1% < 14.1%
Parathyroid hormone <11.0% <22.0% < 14.7%
Phosphorous <5.8% <11.6% < 7.7% 
Plateletcrit <4.8% <9.6% < 6.4%
Platelets      
Platelet distribution wide (PDW) <2.8% <5.7% < 3.8%
Potassium  <2.9%  <5.8% < 3.9%
Progesterone < 13.9% < 27.8% < 18.5%
Prolactin <33.8% <67.5% < 45.0% 
PSA <5.1% <10.2% < 6.8%
PSA, free <5.3% <10.6% < 7.1%
Protein, total <2.0% <3.9% < 2.6%
Reticulocytes <7.3% <14.5% < 9.7%
SHBG <6.7% <13.4% < 8.9%
Sodium <0.4% <0.8% < 0.5%
Testosterone <10.9% <21.8% < 14.5%
Testosterone, free <41.3% <82.5% < 55.0%
Thrombocytes <5.5% <10.9% < 7.3%
Thyroglobulin <8.2% <16.4% < 10.9%
Thyroid stimulating hormone (TSH) <13.4% <26.8% < 17.9%
Thyroxine free  (FT4) <3.6% <7.2% < 4.8%
Thyroxine total (TT4) <4.8% <9.6% < 6.4%
Total tri-iodothyronine (TT3) <4.7% <9.3% < 6.2%
Triiodothyronine (FT3) <3.8% <7.6% < 5.1%
Transferrin <2.9% <5.8%  < 3.9%
Triglycerides  <14.8% <29.5% < 19.7%
Troponin I hs <9.5% <19.0% < 12.7%
Troponin T hs <8.6% <17.1% < 11.4%
Urea Nitrogen <10.0% <20.0%  < 13.3%
Uric acid <6.1% <12.1% < 8.1%
Vitamin A <4.5% <9.0% < 6.0% 
Vitamin E <5.3% <10.6% < 7.1%
Zinc <6.4% <12.8% < 8.5%

Here are the references:

EFLM database, accessed 11/15/2024. https://biologicalvariation.eu/meta_calculations

Performance specifications for measurement uncertainty of common biochemical measurands according to Milan models, Federica Braga and Mauro Panteghini, CCLM 2021; 59(8):1362-1368.

Definition and application of performance specifications for measurement uncertainty of 23 common laboratory tests: linking theory to daily practice. Braga F, Pasqualetti S, Borrillo F, Capoferri A, Chibireva M, Rovegno L, Panteghini M, CCLM 2022 https://doi.org/10.1515/cclm-2022-0806

Redesigning the surveillance of in vitro diagnostic medical devices and of medical laboratory performance by quality control in the traceability era. Mauro Panteghini. CCLM 2022. https://www.degruyter.com/document/doi/10.1515/cclm-2022-1257/html

Measurement Uncertainty of Thyroid Function Tests on a Chemiluminescent Microparticle Immunoassay System Needs to be Improved. Borrillo F, Pasqualetti S, Panteghini M. JALM March 2023 08:02, 420-422. https://academic.oup.com/jalm/article-abstract/8/2/420/6988092?redirectedFrom=fulltext