Analytical interference of intravascular contrast agents with clinical laboratory tests: a joint guideline by the ESUR Contrast Media Safety Committee and the Preanalytical Phase Working Group of the EFLM Science Committee.

The Contrast Media Safety Committee of the European Society of Urogenital Radiology has, together with the Preanalytical Phase Working Group of the EFLM Science Committee, reviewed the literature and updated its recommendations to increase awareness and provide insight into these interferences.

Analytical interference of intravascular contrast agents with clinical laboratory tests: a joint guideline by the ESUR Contrast Media Safety Committee and the Preanalytical Phase Working Group of the EFLM Science Committee.

The Contrast Media Safety Committee of the European Society of Urogenital Radiology has, together with the Preanalytical Phase Working Group of the EFLM Science Committee, reviewed the literature and updated its recommendations to increase awareness and provide insight into these interferences. CLINICAL RELEVANCE STATEMENT: Contrast Media may interfere with clinical laboratory tests. Awareness of potential interference may prevent unwanted misdiagnosis. KEY POINTS: • Contrast Media may interfere with clinical laboratory tests; therefore awareness of potential interference may prevent unwanted misdiagnosis. • Clinical Laboratory tests should be performed prior to radiological imaging with contrast media or alternatively, blood or urine collection should be delayed, depending on kidney function.

The new, race-free, Chronic Kidney Disease Epidemiology Consortium (CKD-EPI) equation to estimate glomerular filtration rate: is it applicable in Europe? A position statement by the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM).

The EFLM recommends not to implement the race-free Chronic Kidney Disease Epidemiology Consortium (CKD-EPI) equation in European laboratories and to keep the 2009 version of the CKD-EPI equation, without applying a race correction factor. This recommendation is completely in line with a recent Editorial published by the European Renal Association who has also proposed to change to a novel equation only when it has considerably better performance, trying to reach global consensus before implementing such a new glomerular filtration rate (GFR) estimation equation. In Europe, this equation could be for instance the new European Kidney Function Consortium (EKFC) equation, which is population-specific, developed from European cohorts and accurate from infants to the older old. Beyond serum creatinine, the estimating equations based on cystatin C will probably gain in popularity, especially because cystatin C seems independent of race. Finally, we must keep in mind that all GFR equations remain an estimation of GFR, especially rough at the individual level. Measuring GFR with a reference method, such as iohexol clearance, remains indicated in specific patients and/or specific situations, and here also, the role of the clinical laboratories is central and should still evolve positively in the future.

Update on apolipoprotein B.

PURPOSE OF REVIEW: The 2019 European Society of Cardiology/European Atherosclerosis Society Guidelines concluded that apolipoprotein B (apoB) was a more accurate measure of cardiovascular risk and a better guide to the adequacy of lipid lowering than low-density lipoprotein cholesterol (LDL-C) or non-high-density lipoprotein cholesterol (HDL-C). Also, they stated that apoB can be measured more accurately than LDL-C or non-HDL-C. This strong endorsement of the central role of apoB contrasts with the limited endorsement of apoB by the 2018 American College of Cardiology/American Heart Association Multisociety Guidelines. Nevertheless, both retained LDL-C as the primary metric to guide statin/ezetimibe/Proprotein convertase subtilisin/kexin type 9 (PCSK9) therapy. RECENT FINDINGS: This essay will review the most important recent advances in knowledge about apoB with particular emphasis on the results of Mendelian randomization studies and a new discordance analysis in subjects on statin therapy. We will also lay out why using LDL-C to guide the adequacy of lipid lowering therapy represents an interpretive error of the results of the statin/ezetimibe/PCSK9 inhibitor randomized clinical trials and therefore why apoB should be the primary metric to guide statin/ezetimibe/PCSK9 therapy. SUMMARY: There is now a robust body of evidence demonstrating the superiority of apoB over LDL-C and non-HDL-C as a clinical marker of cardiovascular risk. LDL-C is not the appropriate marker to assess the benefits of statin/ezetimibe/PCSK9 therapy.

How Well Do Laboratories Adhere to Recommended Guidelines for Cardiac Biomarkers Management in Europe? The CArdiac MARker Guideline Uptake in Europe (CAMARGUE) Study of the European Federation of Laboratory Medicine Task Group on Cardiac Markers.

BACKGROUND: The CARdiac MARker Guideline Uptake in Europe (CAMARGUE) program is a multi-country audit of the use of cardiac biomarkers in routine clinical practice. METHODS: An email link to a web-based questionnaire of 30 multiple-choice questions was distributed via the professional societies in Europe. RESULTS: 374 questionnaires were returned from 39 countries, the majority of which were in northern Europe with a response rate of 8.2%-42.0%. The majority of the respondents were from hospitals with proportionately more responses from central hospitals than district hospitals. Cardiac troponin was the preferred cardiac biomarker, evenly split between cardiac troponin T (cTnT) and cardiac troponin I (cTnI). Aspartate transaminase and lactate dehydrogenase are no longer offered as cardiac biomarkers. Creatine kinase, creatine kinase MB isoenzyme, and myoglobin continue to be offered as part of the cardiac biomarker profile in approximately on 50% of respondents. There is widespread utilization of high sensitivity (hs) troponin assays. The majority of cTnT users measure hs-cTnT. 29.5% of laboratories measure cTnI by a non-hs method but there has been substantial conversion to hs-cTnI. The majority of respondents used ng/L and use the 99th percentile as the upper reference limit (71.9% of respondents). A range of diagnostic protocols are in use. CONCLUSIONS: There is widespread utilization of hs troponin methods. A significant minority do not use the 99th percentile as recommended and there is, as yet, little uptake of very rapid diagnostic strategies. Education of laboratory professionals and clinicians remains a priority.

Quantifying atherogenic lipoproteins for lipid-lowering strategies: consensus-based recommendations from EAS and EFLM.

The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently addressed present and future challenges in the laboratory diagnostics of atherogenic lipoproteins. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDLC), LDL cholesterol (LDLC), and calculated non-HDLC (=total - HDLC) constitute the primary lipid panel for estimating risk of atherosclerotic cardiovascular disease (ASCVD) and can be measured in the nonfasting state. LDLC is the primary target of lipid-lowering therapies. For on-treatment follow-up, LDLC shall be measured or calculated by the same method to attenuate errors in treatment decisions due to marked between-method variations. Lipoprotein(a) [Lp(a)]-cholesterol is part of measured or calculated LDLC and should be estimated at least once in all patients at risk of ASCVD, especially in those whose LDLC declines poorly upon statin treatment. Residual risk of ASCVD even under optimal LDL-lowering treatment should be also assessed by non-HDLC or apolipoprotein B (apoB), especially in patients with mild-to-moderate hypertriglyceridemia (2-10 mmol/L). Non-HDLC includes the assessment of remnant lipoprotein cholesterol and shall be reported in all standard lipid panels. Additional apoB measurement can detect elevated LDL particle (LDLP) numbers often unidentified on the basis of LDLC alone. Reference intervals of lipids, lipoproteins, and apolipoproteins are reported for European men and women aged 20-100 years. However, laboratories shall flag abnormal lipid values with reference to therapeutic decision thresholds.

Non-HDL Cholesterol or apoB: Which to Prefer as a Target for the Prevention of Atherosclerotic Cardiovascular Disease?

PURPOSE OF REVIEW: Guidelines propose using non-HDL cholesterol or apolipoprotein (apo) B as a secondary treatment target to reduce residual cardiovascular risk of LDL-targeted therapies. This review summarizes the strengths, weaknesses, opportunities, and threats (SWOT) of using apoB compared with non-HDL cholesterol. RECENT FINDINGS: Non-HDL cholesterol, calculated as total-HDL cholesterol, includes the assessment of remnant lipoprotein cholesterol, an additional risk factor independent of LDL cholesterol. ApoB is a direct measure of circulating numbers of atherogenic lipoproteins, and its measurement can be standardized across laboratories worldwide. Discordance analysis of non-HDL cholesterol versus apoB demonstrates that apoB is the more accurate marker of cardiovascular risk. Baseline and on-treatment apoB can identify elevated numbers of small cholesterol-depleted LDL particles that are not reflected by LDL and non-HDL cholesterol. ApoB is superior to non-HDL cholesterol as a secondary target in patients with mild-to-moderate hypertriglyceridemia (175-880 mg/dL), diabetes, obesity or metabolic syndrome, or very low LDL cholesterol < 70 mg/dL. When apoB is not available, non-HDL cholesterol should be used to supplement LDLC.

Quantifying Atherogenic Lipoproteins: Current and Future Challenges in the Era of Personalized Medicine and Very Low Concentrations of LDL Cholesterol. A Consensus Statement from EAS and EFLM.

BACKGROUND: The European Atherosclerosis Society-European Federation of Clinical Chemistry and Laboratory Medicine Consensus Panel aims to provide recommendations to optimize atherogenic lipoprotein quantification for cardiovascular risk management. CONTENT: We critically examined LDL cholesterol, non-HDL cholesterol, apolipoprotein B (apoB), and LDL particle number assays based on key criteria for medical application of biomarkers. (a) Analytical performance: Discordant LDL cholesterol quantification occurs when LDL cholesterol is measured or calculated with different assays, especially in patients with hypertriglyceridemia >175 mg/dL (2 mmol/L) and low LDL cholesterol concentrations <70 mg/dL (1.8 mmol/L). Increased lipoprotein(a) should be excluded in patients not achieving LDL cholesterol goals with treatment. Non-HDL cholesterol includes the atherogenic risk component of remnant cholesterol and can be calculated in a standard nonfasting lipid panel without additional expense. ApoB more accurately reflects LDL particle number. (b) Clinical performance: LDL cholesterol, non-HDL cholesterol, and apoB are comparable predictors of cardiovascular events in prospective population studies and clinical trials; however, discordance analysis of the markers improves risk prediction by adding remnant cholesterol (included in non-HDL cholesterol) and LDL particle number (with apoB) risk components to LDL cholesterol testing. (c) Clinical and cost-effectiveness: There is no consistent evidence yet that non-HDL cholesterol-, apoB-, or LDL particle-targeted treatment reduces the number of cardiovascular events and healthcare-related costs than treatment targeted to LDL cholesterol. SUMMARY: Follow-up of pre- and on-treatment (measured or calculated) LDL cholesterol concentration in a patient should ideally be performed with the same documented test method. Non-HDL cholesterol (or apoB) should be the secondary treatment target in patients with mild to moderate hypertriglyceridemia, in whom LDL cholesterol measurement or calculation is less accurate and often less predictive of cardiovascular risk. Laboratories should report non-HDL cholesterol in all standard lipid panels.

Evaluation of four hemoglobin separation analyzers for hemoglobinopathy diagnosis.

BACKGROUND: Four automated hemoglobin separation devices are compared in their ability to detect hemoglobinopathies, both in HbA1c and in hemoglobinopathy mode. METHODS: Quality control material and 58 samples, including one heterozygous α-thalassemia sample, six heterozygote ß-thalassemia samples and 32 samples with a known hemoglobin variant, were used to assess imprecision of HbF and HbA2 measurements, correlation with the gold standard and sensitivity for detecting ß-thalassemia and Hb variants on D-100 (Bio-Rad Laboratories), HA 8180T (Menarini), HLC-723G8 (Tosoh Bioscience) and Capillarys 2 Flex Piercing (Sebia). RESULTS: Imprecision was <10% for both HbF and HbA2 in all modes of all analyzers. Correlation studies for HbF and HbA2 demonstrated statistically significant but small biases when compared to the gold standard. All six ß-thalassemia samples but one were detected on all analyzers using a HbA2 cut-off value of 3.5%. D-100, HA8180T and the Hb-pathy mode of the HLC-723G8 and the Capillarys are able to detect the most common important Hb variants (Hb C, D, E and S), but more seldom variants can be missed as they co-elute with HbA0. The HbA1c mode of the Capillarys correctly detected all measured hemoglobin variants and can therefore be used as a hemoglobinopathy screening device. This was also the case for the most common important Hb variants on the HbA1c mode of the HLC-723G8, but two rare variants were not detected. CONCLUSION: This study stresses the importance for individual laboratories to know the advantages and drawbacks of their hemoglobin separation analyzer and its different modes in the diagnosis of hemoglobinopathies.

Which Lipids Should Be Analyzed for Diagnostic Workup and Follow-up of Patients with Hyperlipidemias?

PURPOSE OF REVIEW: To summarize and discuss the clinical use of lipid and apolipoprotein tests in the settings of diagnosis and therapeutic follow-up of hyperlipidemia. RECENT FINDINGS: The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently produced recommendations on the measurement of atherogenic lipoproteins, taking into account the strengths and weaknesses of analytical and clinical performances of the tests. Total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, and calculated non-HDL cholesterol (= LDL + remnant cholesterol) constitute the primary lipid panel for hyperlipidemia diagnosis and cardiovascular risk estimation. LDL cholesterol is the primary target of lipid-lowering therapies. Non-HDL cholesterol or apolipoprotein B should be used as secondary therapeutic target in patients with mild-to-moderate hypertriglyceridemia, 2-10 mmol/l (175-880 mg/dl). Lipoprotein (a) is included in LDL cholesterol and should be measured at least once in all patients at cardiovascular risk, including to explain poor response to statin treatment.

Could accreditation bodies facilitate the implementation of medical guidelines in laboratories?

Several studies have shown that recommendations related to how laboratory testing should be performed and results interpreted are limited in medical guidelines and that the uptake and implementation of the recommendations that are available need improvement. The EFLM/UEMS Working Group on Guidelines conducted a survey amongst the national societies for clinical chemistry in Europe regarding development of laboratory-related guidelines. The results showed that most countries have guidelines that are specifically related to laboratory testing; however, not all countries have a formal procedure for accepting such guidelines and few countries have guideline committees. Based on this, the EFLM/UEMS Working Group on Guidelines conclude that there is still room for improvement regarding these processes in Europe and raise the question if the accreditation bodies could be a facilitator for an improvement.

Fasting is not routinely required for determination of a lipid profile: clinical and laboratory implications including flagging at desirable concentration cut-points-a joint consensus statement from the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine.

AIMS: To critically evaluate the clinical implications of the use of non-fasting rather than fasting lipid profiles and to provide guidance for the laboratory reporting of abnormal non-fasting or fasting lipid profiles. METHODS AND RESULTS: Extensive observational data, in which random non-fasting lipid profiles have been compared with those determined under fasting conditions, indicate that the maximal mean changes at 1-6 h after habitual meals are not clinically significant [+0.3 mmol/L (26 mg/dL) for triglycerides; -0.2 mmol/L (8 mg/dL) for total cholesterol; -0.2 mmol/L (8 mg/dL) for LDL cholesterol; +0.2 mmol/L (8 mg/dL) for calculated remnant cholesterol; -0.2 mmol/L (8 mg/dL) for calculated non-HDL cholesterol]; concentrations of HDL cholesterol, apolipoprotein A1, apolipoprotein B, and lipoprotein(a) are not affected by fasting/non-fasting status. In addition, non-fasting and fasting concentrations vary similarly over time and are comparable in the prediction of cardiovascular disease. To improve patient compliance with lipid testing, we therefore recommend the routine use of non-fasting lipid profiles, while fasting sampling may be considered when non-fasting triglycerides >5 mmol/L (440 mg/dL). For non-fasting samples, laboratory reports should flag abnormal concentrations as triglycerides ≥2 mmol/L (175 mg/dL), total cholesterol ≥5 mmol/L (190 mg/dL), LDL cholesterol ≥3 mmol/L (115 mg/dL), calculated remnant cholesterol ≥0.9 mmol/L (35 mg/dL), calculated non-HDL cholesterol ≥3.9 mmol/L (150 mg/dL), HDL cholesterol ≤1 mmol/L (40 mg/dL), apolipoprotein A1 ≤1.25 g/L (125 mg/dL), apolipoprotein B ≥1.0 g/L (100 mg/dL), and lipoprotein(a) ≥50 mg/dL (80th percentile); for fasting samples, abnormal concentrations correspond to triglycerides ≥1.7 mmol/L (150 mg/dL). Life-threatening concentrations require separate referral when triglycerides >10 mmol/L (880 mg/dL) for the risk of pancreatitis, LDL cholesterol >13 mmol/L (500 mg/dL) for homozygous familial hypercholesterolaemia, LDL cholesterol >5 mmol/L (190 mg/dL) for heterozygous familial hypercholesterolaemia, and lipoprotein(a) >150 mg/dL (99th percentile) for very high cardiovascular risk. CONCLUSION: We recommend that non-fasting blood samples be routinely used for the assessment of plasma lipid profiles. Laboratory reports should flag abnormal values on the basis of desirable concentration cut-points. Non-fasting and fasting measurements should be complementary but not mutually exclusive.

How Well Do Laboratories Adhere to Recommended Clinical Guidelines for the Management of Myocardial Infarction: The CARdiac MArker Guidelines Uptake in Europe Study (CARMAGUE).

BACKGROUND: We undertook an assessment of current use of evidence-based guidelines for the use of cardiac biomarkers in Europe (EU) and North America (NA). METHODS: In 2013-2014 a web-based questionnaire was distributed via NA and EU biochemical societies. Questions covered cardiac biomarkers measured, analytical methods used, decision thresholds, and use of decision-making protocols. Results were collated using a central database and analyzed using comparative and descriptive nonparametric statistics. RESULTS: In EU, returns were obtained from 442 hospitals, 50% central or university hospitals, and 39% from local hospitals from 35 countries with 395/442 (89%) provided an acute service. In NA there were 91 responses (63.7% central or university hospitals, 19.8% community hospitals) with 76/91 (83.5%) providing an acute service. Cardiac troponin was the preferred cardiac biomarker in 99.5% (EU) and 98.7% (NA), and the first line marker in 97.7% (EU) and 97.4% (NA). There were important differences in the choice of decision limits and their derivations. The origin of the information was also significantly different, with EU vs NA as follows: package insert, 61.9% vs 40%; publications, 17.1% vs 15.0%; local clinical or analytical validation choice, 21.0% vs 45.0%; P = 0.0003. CONCLUSIONS: There are significant differences between EU and NA use of cardiac biomarkers. This probably relates to different availability of assays between EU and NA (such as high-sensitivity troponin assays) and different laboratory practices on assay introduction (greater local evaluation of assay performance occurred in NA).

Fasting Is Not Routinely Required for Determination of a Lipid Profile: Clinical and Laboratory Implications Including Flagging at Desirable Concentration Cutpoints-A Joint Consensus Statement from the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine.

AIMS: To critically evaluate the clinical implications of the use of non-fasting rather than fasting lipid profiles and to provide guidance for the laboratory reporting of abnormal non-fasting or fasting lipid profiles. METHODS AND RESULTS: Extensive observational data, in which random non-fasting lipid profiles have been compared with those determined under fasting conditions, indicate that the maximal mean changes at 1-6 h after habitual meals are not clinically significant [+0.3 mmol/L (26 mg/dL) for triglycerides; -0.2 mmol/L (8 mg/dL) for total cholesterol; -0.2 mmol/L (8 mg/dL) for LDL cholesterol; +0.2 mmol/L (8 mg/dL) for calculated remnant cholesterol; -0.2 mmol/L (8 mg/dL) for calculated non-HDL cholesterol]; concentrations of HDL cholesterol, apolipoprotein A1, apolipoprotein B, and lipoprotein(a) are not affected by fasting/non-fasting status. In addition, non-fasting and fasting concentrations vary similarly over time and are comparable in the prediction of cardiovascular disease. To improve patient compliance with lipid testing, we therefore recommend the routine use of non-fasting lipid profiles, whereas fasting sampling may be considered when non-fasting triglycerides are >5 mmol/L (440 mg/dL). For non-fasting samples, laboratory reports should flag abnormal concentrations as triglycerides ≥2 mmol/L (175 mg/dL), total cholesterol ≥5 mmol/L (190 mg/dL), LDL cholesterol ≥3 mmol/L (115 mg/dL), calculated remnant cholesterol ≥0.9 mmol/L (35 mg/dL), calculated non-HDL cholesterol ≥3.9 mmol/L (150 mg/dL), HDL cholesterol ≤1 mmol/L (40 mg/dL), apolipoprotein A1 ≤1.25 g/L (125 mg/dL), apolipoprotein B ≥1.0 g/L (100 mg/dL), and lipoprotein(a) ≥50 mg/dL (80th percentile); for fasting samples, abnormal concentrations correspond to triglycerides ≥1.7 mmol/L (150 mg/dL). Life-threatening concentrations require separate referral for the risk of pancreatitis when triglycerides are >10 mmol/L (880 mg/dL), for homozygous familial hypercholesterolemia when LDL cholesterol is >13 mmol/L (500 mg/dL), for heterozygous familial hypercholesterolemia when LDL cholesterol is >5 mmol/L (190 mg/dL), and for very high cardiovascular risk when lipoprotein(a) >150 mg/dL (99th percentile). CONCLUSIONS: We recommend that non-fasting blood samples be routinely used for the assessment of plasma lipid profiles. Laboratory reports should flag abnormal values on the basis of desirable concentration cutpoints. Non-fasting and fasting measurements should be complementary but not mutually exclusive.

Why are clinical practice guidelines not followed?

Clinical practice guidelines (CPG) are written with the aim of collating the most up to date information into a single document that will aid clinicians in providing the best practice for their patients. There is evidence to suggest that those clinicians who adhere to CPG deliver better outcomes for their patients. Why, therefore, are clinicians so poor at adhering to CPG? The main barriers include awareness, familiarity and agreement with the contents. Secondly, clinicians must feel that they have the skills and are therefore able to deliver on the CPG. Clinicians also need to be able to overcome the inertia of "normal practice" and understand the need for change. Thirdly, the goals of clinicians and patients are not always the same as each other (or the guidelines). Finally, there are a multitude of external barriers including equipment, space, educational materials, time, staff, and financial resource. In view of the considerable energy that has been placed on guidelines, there has been extensive research into their uptake. Laboratory medicine specialists are not immune from these barriers. Most CPG that include laboratory tests do not have sufficient detail for laboratories to provide any added value. However, where appropriate recommendations are made, then it appears that laboratory specialist express the same difficulties in compliance as front-line clinicians.

Evaluation of Three Hemoglobin A1c Point-of-Care Instruments.

BACKGROUND: Hemoglobin A1c is currently used both for monitoring and diagnosing patients with diabetes mellitus. Point-of-care (POC) instruments have been proposed to improve glycemic control of patients with diabetes by providing a rapid result if the analytical performance is acceptable. However, the performance of most current POC devices is unsatisfactory. In this study, we evaluated 3 POC devices: cobas b101 (Roche), Afinion (Alere) and B-Analyst (Menarini). METHODS: The CLSI protocols EP-5 and EP-9 were applied to investigate precision, accuracy, and bias. Bias was compared with an ion-exchange chromatography method (Adams Arkray HA-8160, Menarini) of which the accuracy was assessed by three secondary reference methods (SRMs) and a capillary zone electrophoresis-based laboratory method (Capillarys Flex Piercing 2, Sebia). RESULTS: Using the IFCC units (mmol/mol), total CV's for cobas b101, Afinion and B-Analyst ranged from 2.0 to 3.9%, from 2.3 to 3.7% and from 2.3 to 2.9%, respectively, compared to a total CV ranging from 0.9 to 1.2% for the Adams Arkray HA-8160. A high correlation was found between the HA-8160 and the three POC devices (r = 0.992, r = 0.968, r = 0.998 for cobas b101, Afinion and B-Analyst, respectively). However, all three showed a significant bias of -2.2 mmol/mol, -2.2 mmol/mol and 0.5 mmol/mol, respectively. CONCLUSIONS: Only the B-Analyst met the current HbA1c quality specifications for precision, whereas cobas b101 and Afinion failed on the low level. Significant bias was observed for all three POC instruments. As low precision and bias are required for both monitoring and diagnosis of diabetes, we believe that POC devices should be carefully selected.

Associations between dietary inflammatory index and inflammatory markers in the Asklepios Study.

Previous research has shown that nutrients and certain food items influence inflammation. However, little is known about the associations between diet, as a whole, and inflammatory markers. In the present study, we examined the ability of a FFQ-derived dietary inflammatory index (DII) to predict inflammation. Data from a Belgian cross-sectional study of 2524 generally healthy subjects (age 35-55 years) were used. The DII is a population-based, literature-derived dietary index that was developed to predict inflammation and inflammation-related chronic diseases. The DII was calculated from FFQ-derived dietary information and tested against inflammatory markers, namely C-reactive protein (CRP), IL-6, homocysteine and fibrinogen. Analyses were performed using multivariable logistic regression, adjusting for energy, age, sex, BMI, smoking status, education level, use of non-steroidal anti-inflammatory drugs, blood pressure, use of oral contraceptives, anti-hypertensive therapy, lipid-lowering drugs and physical activity. Multivariable analyses showed significant positive associations between the DII and the inflammatory markers IL-6 (>1·6 pg/ml) (OR 1·19, 95 % CI 1·04, 1·36) and homocysteine (>15 µmol/l) (OR 1·56, 95 % CI 1·25, 1·94). No significant associations were observed between the DII and the inflammatory markers CRP and fibrinogen. These results reinforce the fact that diet, as a whole, plays an important role in modifying inflammation.

Proteolysis is a confounding factor in the interpretation of faecal calprotectin.

BACKGROUND: Calprotectin is a 36 kDa calcium and zinc binding protein. An increased level of calprotectin points towards inflammatory bowel disease. However, the biomarker calprotectin shows 14 potential cleavages sites for trypsin. Next to trypsin, also the presence of its inhibitor α1-antitrypsin after a gastrointestinal bleeding may affect calprotectin testing. In this study, effects of trypsin and α1-antitrypsin as potential confounders for faecal calprotectin testing are investigated. METHODS: An in vitro model was created. As calprotectin source, leukocytes were isolated and subsequently lysed (1% Triton X-100) and diluted in faecal matrix. Trypsin digestion was carried out by adding trypsin. Incubation occurred for 24 h or 48 h (37 °C). To study the influence of α1-antitrypsin on trypsin, the same experiment was repeated after adding serum containing α1-antitrypsin. RESULTS: In vitro experiments enabled monitoring of the faecal calprotectin digestion, leading to loss of immunoreactivity. Trypsin activity was a potential confounder in the interpretation of calprotectin, in particular for proximal lesions, where exposure of calprotectin to trypsin is prolonged. Relative calprotectin loss was proportional to the amount of trypsin. Decrease of calprotectin was more pronounced after 48 h of incubation in comparison to 24 h of incubation. Analogue experiments also showed stable calprotectin values after adding α1-antitrypsin. CONCLUSIONS: Transit time, trypsin activity and addition of blood as a source of α1-antitrypsin may be regarded as potential confounders in the interpretation of calprotectin results. Age-related cut-off values depending on the anatomical localisation of the lesions could improve the diagnostic efficiency of calprotectin testing.