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(1) Background: Many vaccines require higher, additional doses or adjuvants to provide adequate protection for people living with HIV (PLWH). Despite their potential risk of severe coronavirus disease 2019, immunological data remain sparse, and a clear consensus for the best booster strategy is lacking. (2) Methods: Using the data obtained from our previous study assessing prospective T-cell and humoral immune responses before and after administration of a third dose of SARS-CoV-2 vaccine, we assessed the correlations between immune parameters reflecting humoral and cellular immune responses. We further aimed at identifying distinct clusters of patients with similar patterns of immune response evolution to determine how these relate to demographic and clinical factors. (3) Results: Among 80 PLWH and 51 healthcare workers (HCWs) enrolled in the study, cluster analysis identified four distinct patterns of evolution characterised by specific immune patterns and clinical factors. We observed that immune responses appeared to be less robust in cluster A, whose individuals were mostly PLWH who had never been infected with SARS-CoV-2. Cluster C, whose individuals showed a particularly drastic increase in markers of humoral immune response following the third dose of vaccine, was mainly composed of female participants who experienced SARS-CoV-2. Regarding the correlation study, although we observed a strong positive correlation between markers mirroring humoral immune response, markers of T-cell response following vaccination correlated only in a lesser extent with markers of humoral immunity. This suggests that neutralising antibody titers alone are not always a reliable reflection of the magnitude of the whole immune response. (4) Conclusions: Our findings show heterogeneity in immune responses among SARS-CoV-2 vaccinated PLWH. Specific subgroups could therefore benefit from distinct immunization strategies. Prior or breakthrough natural infection enhances the activity of vaccines and must be taken into account for informing global vaccine strategies among PLWH, even those with a viro-immunologically controlled infection.

Objectives: Detection of antinuclear antibodies (ANA) by indirect immunofluorescence assay using HEp-2 cells (HEp-2 IFA) is used to screen for various autoimmune diseases. HEp-2 IFA suffers from variability, which hampers harmonization., Methods: A questionnaire was developed to collect information on HEp-2 IFA methodology, computer-assisted diagnosis (CAD) systems, training, inter-observer variability, quality assessment, reagent lot change control, and method verification. The questionnaire was distributed to laboratories by Sciensano (Belgium), national EASI groups (Italy, Croatia, Portugal, Estonia, Greece) and ICAP (worldwide). Answers were obtained by 414 laboratories. The results were analysed in the framework of the recent EFLM/EASI/ICAP ANA recommendations (companion paper)., Results: Laboratories used either HEp-2, HEp-2000, or HEp-20-10 cells and most laboratories (80%) applied the same screening dilution for children and adults. The conjugate used varied between laboratories [IgG-specific (in 57% of laboratories) vs. polyvalent]. Sixty-nine percent of CAD users reviewed the automatic nuclear pattern and 53% of CAD users did not fully exploit the fluorescence intensity for quality assurance. Internal quality control was performed by 96% of the laboratories, in 52% of the laboratories only with strongly positive samples. Interobserver variation was controlled by 79% of the laboratories. Limited lot-to-lot evaluation was performed by 68% of the laboratories. Method verification was done by 80% of the respondents., Conclusions: Even though many laboratories embrace high-quality HEp-2 IFA, substantial differences in how HEp-2 IFA is performed and controlled remain. Acting according to the EFLM/EASI/ICAP ANA recommendations can improve the global performance and quality of HEp-2 IFA and nurture harmonization., (© 2023 Walter de Gruyter GmbH, Berlin/Boston.)

Background: The faecal calprotectin (FC) measurement is used for inflammatory bowel disease (IBD) diagnosis and follow-up. The aim of this study was to validate for the first time the new IDS FC extraction device and immunoassay kit, and to compare it with the DiaSorin test in patients with and without IBD. Methods: First, the precision of the IDS assay and its stability were assessed. Then, 379 stool extracts were analysed with the IDS kit on iSYS and compared with a DiaSorin Liaison XL assay. Results: The intra- and inter-assay CVs did not exceed 5%. The stool samples were stable up to 4 weeks at −20 °C. Lot-to-lot comparison showed a good correlation (Lot1 = 1.06 × Lot2 + 0.60; p > 0.05). The Passing and Bablok regression showed no significant deviation from linearity between the two methods (IDS = 1.06 × DiaSorin − 0.6; p > 0.05; concordance correlation coefficient = 0.93). According to the recommended cut-offs, the IDS assay identified more IBD and irritable bowel syndrome patients than DiaSorin, which had more borderline results (16 vs. 20%, respectively). Conclusions: The IDS faecal calprotectin had good analytical validation parameters. Compared to the DiaSorin method, it showed comparable results, but slightly outperformed it in the identification of more IBD patients and active disease.

Background: Understanding and measuring the individual level of immune protection and its persistence at both humoral and cellular levels after SARS-CoV-2 vaccination is mandatory for the management of the vaccination booster campaign. Our prospective study was designed to assess the immunogenicity of the BNT162b2 mRNA vaccine in triggering the cellular and humoral immune response in healthcare workers up to 12 months after the initial vaccination, with one additional boosting dose between 6 and 12 months., Methods: This prospective study enrolled 208 healthcare workers (HCWs) from the Liège University Hospital (CHU) of Liège in Belgium. Participants received two doses of BioNTech/Pfizer COVID-19 vaccine (BNT162b2) and a booster dose 6-12 months later. Fifty participants were SARS-CoV-2 experienced and 158 were naïve before the vaccination. Blood sampling was performed at the day of the first (T0) and second (T1) vaccine doses administration, then at 2 weeks (T2), 4 weeks (T3), 6 months (T4) and 12 months (T5) after the second dose. Between T4 and T5, participants also got the third boosting vaccine dose. A total of 1145 blood samples were collected. All samples were tested for the presence of anti-Spike antibodies, using the DiaSorin LIAISON SARS-CoV-2 Trimeric S IgG assay, and for anti-Nucleocapsid antibodies, using Elecsys anti-SARS-CoV-2 assay​​. Neutralizing antibodies against the SARS-CoV-2 Wuhan-like variant strain were quantified in all samples using a Vero E6 cell-based neutralization assay. Cell-mediated immune response was evaluated at T4 and T5 on 80 and 55 participants, respectively, by measuring the secretion of IFN-γ on peripheral blood lymphocytes using the QuantiFERON Human IFN-γ SARS-CoV-2, from Qiagen. We analyzed separately the naïve and experienced participants., Findings: We found that anti-spike antibodies and neutralization capacity levels were significantly higher in SARS-CoV-2 experienced HCWs compared to naïve HCWs at all time points analyzed except the one after boosting dose. Cellular immune response was also higher in experienced HCWs six months following vaccination. Besides the impact of SARS-CoV-2 infection history on immune response to BNT162b2 mRNA vaccine, we observed a significant negative association between age and persistence of humoral response. The booster dose induced an increase in humoral and cellular immune responses, particularly in naive individuals. Breakthrough infections resulted in higher cellular and humoral responses after the booster dose., Conclusions: Our data strengthen previous findings demonstrating that immunization through vaccination combined with natural infection is better than 2 vaccine doses immunization or natural infection alone. The benefit of the booster dose was greater in naive individuals. It may have implications for personalizing mRNA vaccination regimens used to prevent severe COVID-19 and reduce the impact of the pandemic on the healthcare system. More specifically, it may help prioritizing vaccination, including for the deployment of booster doses., Competing Interests: Authors FB and LG are the inventors of the device used in the saliva collection kit. This device was patented (EP20186086.3) and produced by Diagenode (Seraing, Belgium) under a commercial agreement with the University of Liège. This does not alter the adherence to all journal policies on sharing data and materials. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Desmecht, Tashkeev, El Moussaoui, Marechal, Perée, Tokunaga, Fombellida-Lopez, Polese, Legrand, Wéry, Mni, Fouillien, Toussaint, Gillet, Bureau, Lutteri, Hayette, Moutschen, Meuris, Vermeersch, Desmecht, Rahmouni and Darcis.)

Purpose: To emphasize physio-pathological, clinical and prognosis differences between conditions causing serious and sometimes very similar clinical manifestations: anti-aquaporin-4 (AQP4) and anti-myelin oligodendrocyte glycoprotein (MOG) antibodies related diseases, and seronegative NMOSD (neuromyelitis optica spectrum disorders)., Methods: Based on Wingerchuk et al. (Neurology 85:177-189, 2015) criteria for NMOSD and on those more recently proposed by Jarius et al. (J Neuroinflammation 15:134, 2018) for MOGAD (MOG associated disorders), we retrospectively surveyed 10 AQP4-NMOSD, 8 MOGAD and 2 seronegative NMOSD, followed at the specialized neuroimmunology unit of the CHU Liège., Results: Female predominance was only observed in AQP4 group. Age at onset was 37.8 and 27.7 years old for AQP4-NMOSD and MOGAD respectively. In both groups, the first clinical event most often consisted of optic neuritis (ON), followed by isolated myelitis. Fifteen of our 20 patients encountered a relapsing course with 90% relapses in AQP4-NMOSD, 62.5% in MOGAD and 50% in seronegative group, and a mean period between first and second clinical event of 7.1 and 4.8 months for AQP4-NMOSD and MOGAD, respectively. In total we counted 54 ON, with more ON per patient in MOGAD. MOG-associated ON mainly affected the anterior part of the optic nerve with a papilledema in 79.2% of cases. Despite a fairly good visual outcome after MOG-associated ON, retinal nerve fibre layer (RNFL) thickness decreased, suggesting a fragility of the optic nerve toward further attacks., Conclusion: As observed in larger cohorts, our MOGAD and AQP4-NMOSD cases differ by clinical and prognostic features. A better understanding of these diseases should encourage prompt biological screening and hasten proper diagnosis and treatment., (© 2021. The Author(s).)

Neurological paraneoplastic syndromes are non-metastatic complications of systemic cancers, often resulting from an immune response triggered by the crossed expression of neuronal antigens by tumour cells. Several neurological syndromes such as cerebellar degeneration, sensory neuronopathy, limbic encephalitis, encephalomyelitis or the Lambert-Eaton myasthenic syndrome are most often paraneoplastic and require prompt cancer screening, particularly if the patient shows risk factors for cancer. Although there are many exceptions to this rule, a given syndrome is often associated with a particular antibody and the corresponding tumour. A prompt diagnosis of neurological paraneoplastic syndrome is of major importance as it often reveals the underlying tumour. The treatment relies on both the elimination of the neoplasia and the control of the immune response.

Background: Proteinuria has been commonly reported in patients with COVID-19. However, only dipstick tests have been frequently used thus far. Here, the quantification and characterization of proteinuria were investigated and their association with mortality was assessed., Methods: This retrospective, observational, single center study included 153 patients, hospitalized with COVID-19 between March 28th and April 30th, 2020, in whom total proteinuria and urinary α 1 -microglobulin (a marker of tubular injury) were measured. Association with mortality was evaluated, with a follow-up until May 7th, 2020., Results: According to the Kidney Disease Improving Global Outcomes staging, 14% (n = 21) of the patients had category 1 proteinuria (< 150 mg/g of urine creatinine), 42% (n = 64) had category 2 (between 150 and 500 mg/g) and 44% (n = 68) had category 3 proteinuria (over 500 mg/g). Urine α 1 -microglobulin concentration was higher than 15 mg/g in 89% of patients. After a median follow-up of 27 [14;30] days, the mortality rate reached 18%. Total proteinuria and urinary α 1 -microglobulin were associated with mortality in unadjusted and adjusted models. This association was stronger in subgroups of patients with normal renal function and without a urinary catheter., Conclusions: Proteinuria is frequent in patients with COVID-19. Its characterization suggests a tubular origin, with increased urinary α 1 -microglobulin. Tubular proteinuria was associated with mortality in COVID-19 in our restropective, observational study.

Background: The International Consensus on Antinuclear Antibody (ANA) Patterns (ICAP) has recently proposed nomenclature in order to harmonize ANA indirect immunofluorescence (IIF) pattern reporting. ICAP distinguishes competent-level from expert-level patterns. A survey was organized to evaluate reporting, familiarity, and considered clinical value of ANA IIF patterns., Methods: Two surveys were distributed by European Autoimmunity Standardization Initiative (EASI) working groups, the International Consensus on ANA Patterns (ICAP) and UK NEQAS to laboratory professionals and clinicians., Results: 438 laboratory professionals and 248 clinicians from 67 countries responded. Except for dense fine speckled (DFS), the nuclear competent patterns were reported by > 85% of the laboratories. Except for rods and rings, the cytoplasmic competent patterns were reported by > 72% of laboratories. Cytoplasmic IIF staining was considered ANA positive by 55% of clinicians and 62% of laboratory professionals, with geographical and expertise-related differences. Quantification of fluorescence intensity was considered clinically relevant for nuclear patterns, but less so for cytoplasmic and mitotic patterns. Combining IIF with specific extractable nuclear antigens (ENA)/dsDNA antibody testing was considered most informative. Of the nuclear competent patterns, the centromere and homogeneous pattern obtained the highest scores for clinical relevance and the DFS pattern the lowest. Of the cytoplasmic patterns, the reticular/mitochondria-like pattern obtained the highest scores for clinical relevance and the polar/Golgi-like and rods and rings patterns the lowest., Conclusion: This survey confirms that the major nuclear and cytoplasmic ANA IIF patterns are considered clinically important. There is no unanimity on classifying DFS, rods and rings and polar/Golgi-like as a competent pattern and on reporting cytoplasmic patterns as ANA IIF positive.

Introduction: Determination of creatinine and estimation of Glomerular Filtration Rate (GFR) rapidly before injection of contrast media provides early detection of high-risk patients for acute kidney failure. Hence, a rapid point-of-care (POC) device (result in 30 s) allowing creatinine measurement and eGFR could be of interest. To validate this method, we considered a population referred for measuring GFR., Methods: Iohexol plasma clearance was used to measure GFR. For each subject, enzymatic creatinine was quantified with two different devices: in plasma with the Roche Cobas analyzer and in capillary blood with the Nova Biomedical POC device. Both values of creatinine were used in the CKD-EPI equation for estimated glomerular filtration rate (eGFR). eGFR using POC was compared to eGFR using Cobas and to mGFR by Passing Bablok regression, calculation of bias, precision and accuracy (or concordance) within 30%. Also, we calculated the rate of discrepant staging (eGFR >60 or ≤ 60 when mGFR is actually ≤60 and > 60) with both creatinine methods., Results: 120 subjects (52 ± 13 years, 49% of women) were included. Mean mGFR was 77 ± 27 mL/min/1.73m 2 with 29 patients presenting mGFR <60 mL/min/1.73m 2 . Passing- Bablok regression comparing eGFR obtained with the POC and the Cobas was: eGFR POC  = -0.1 (95% CI: -7.4; 3.0) + 1.06 (95% CI: 1.00; 1.15) x eGFR COBAS . Mean bias was 3.7 ± 14.1 mL/min/1.73m 2 . Concordance within 30% was 82%. Compared to mGFR, Passing-Bablok with POC was: eGFR POC  = -11.5 (95% CI: -22.9; -0.7) + 1.15 (95% CI: 1.02; 1.29) x mGFR. Mean bias was 0.1 ± 17.6 mL/min/1.73m 2 . Accuracy within 30% was 81%. Between eGFR COBAS and mGFR, mean bias was -3.7 ± 12.5 mL/min/1.73m 2 . Accuracy within 30% was 95%. With POC (and Cobas), 3.3% (0.8%) of patients would have been considered with GFR > 60 mL/min/1.73m 2 whereas mGFR it was ≤60 and 10% (9.2%) of them would have been considered with GFR ≤60 mL/min/1.73m 2 when mGFR was >60., Conclusion: Creatinine measured with the POC has an acceptable performance when used with the CKD-EPI equation to estimate GFR. Its ability to detect GFR <60 mL/min/1.73m 2 is not significantly different from the classical Roche assay. StatSensor Creatinine (Nova Biomedical) can be used for GFR screening before contrast media injection., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Serum kappa and lambda free light chains (FLC) are useful in the diagnosis, prognosis and monitoring of patients with monoclonal gammopathies. The Binding Site and Siemens were the only suppliers of kits for these analyses until recently, when Sebia introduced an enzyme-linked immunosorbent assay (ELISA) on an automated instrument, DAS AP22 ELITE., Method: Samples from routine analysis, controls and chronic kidney disease (CKD) patients were tested using the automated version of Sebia FLC ELISA with the AP22 ELITE and results were compared with Freelite on the SPA PLUS (The Binding Site)., Results: Sebia FLC ELISA showed a good performance using the AP22 ELITE. A concordance of 82% was found with the results obtained with Freelite. Sebia FLC is a reproducible assay, requiring less retesting than Freelite thanks to a broader range. Earlier findings that the results obtained are closer to the FLC monoclonal band measured by electrophoresis were confirmed. Higher kappa and lambda values obtained in CKD individuals were also shown, confirming that a kappa/lambda FLC ratio should be introduced by Sebia for CKD patients, as with The Binding Site., Conclusions: Sebia put forward new technology that automatically measures free light chains. This technique is suitable for routine use; however, the results cannot be used interchangeably with Freelite kits., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Although it remained controversial for a long time, central nervous system (CNS) involvement of graft-versus-host disease (GVHD) is now becoming recognized as a real nosological entity. Previous case reports have suggested heterogeneous clinical presentations and it is not excluded that the whole spectrum of manifestations has not yet been fully described. Here, we report the case of a 58-year-old man with chronic GVHD who developed a rapidly ingravescent encephalopathy. There was no evidence for CNS immune-mediated lesions on conventional imaging nor for cellular infiltration in the cerebrospinal fluid. Serum analyses revealed the presence of anti-neuronal antibodies directed against anti-contactin-associated protein 2 (anti-Caspr2), a protein associated with voltage-gated potassium neuronal channels. Functional imaging with 2-deoxy-2-[fluorine-18] fluoro- d-glucose integrated with computed tomography (18F-FDG PET-CT) demonstrated diffuse cortical and subcortical hypometabolism. The patient was treated with a combination of immunosuppressive agents (corticosteroids, cyclophosphamide and rituximab) and progressively recovered normal neurocognitive functions. Taken together, these data suggest that CNS-GVHD may manifest as a reversible antibody-mediated functional encephalopathy. This report suggests for the first time the interest of screening for anti-neuronal antibodies and functional imaging with brain 18F-FDG PET-CT in diagnosing this severe complication of allogeneic hematopoietic cell transplantation (alloHSCT)., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The measurement of proteinuria is a very simple tool to screen and manage kidney diseases. Its predictive role is also relevant from a cardiovascular point of view. However, the interpretation of the results is not always easy. Indeed, there are several different methods to detect or measure proteinuria (or albuminuria), varying from the measurement on a 24-hour urine collection to the simplest detection with dipsticks or measurement on a random urine sample. Some methods are measuring total proteins, whereas others are measuring more specifically albuminuria. For all methods, pitfalls exist and will be discussed. A positive result must be confirmed by a quantitative measurement on 24-hour collection or on a first morning sample (this last one can only be interpreted as a ratio to urinary creatinine excretion). Lastly, we will briefly discuss the management of a patient with a new diagnosis of proteinuria (or albuminuria).

Objective: The conversion of Hashimoto's thyroiditis (HT) to hyperthyroidism due to thyrotropin receptor antibodies is intriguing and considered rare. The contribution of TSH receptor blocking antibodies (TRAb), which may be stimulators (TSAb) or blockers (TBAb), is suspected. We describe clinical and biological variables in a series of patients switching from Hashimoto's thyroiditis to Grave's disease., Subjects and Methods: Retrospective case study of 24 patients with Hashimoto's thyroiditis followed during 48 ± 36 months that developed later Graves' disease (GD). These variables were analysed in the hypo and hyperthyroid phase: age, sex, initial TSH, free triiodothyronine (fT3), free thyroxine (fT4), anti-TPO, TBII antibodies, parietal cell autoantibodies, time between hypo and hyperthyroidism, thyroid volume and levothyroxine doses (LT)., Results: In HT, mean TSH was 9.4 ± 26.1 UI/L and levothyroxine treatment was 66.2 ± 30.8 µg/day. The switch to GD was observed 38 ± 45 months after HT diagnosis. As expected, we found significant differences on TSH, FT3, FT4 and TBAb levels. Three out of 14 patients had parietal cell autoantibodies. In two of these three cases there was an Helicobacter pylori infection. There were no significant differences between HT and GD groups with respect to thyroid volume., Conclusions: To our knowledge, large series documenting the conversion of HT to GD are scarce. Although rare, this phenomenon should not be misdiagnosed. Suspicion should be raised whenever thyroxine posology must be tapered down during the follow-up of HT patients. Further immunological and genetic studies are needed to explain this unusual autoimmune change.

Adipsic diabetes insipidus is a rare complication of intracranial tumors in which impaired antidiuretic hormone secretion is associated with the loss of thirst sensation. Here, we present the case of a patient with bifocal intracranial germinoma, diagnosed due to symptoms mainly caused by adipsic diabetes insipidus. This is, to our knowledge, the first case of adipsic diabetes insipidus revealing an intracranial germinoma reported in the literature. We describe the diagnostic procedures and the three-year follow-up of this patient. Management of intracranial germ-cell tumors is made complex by the wide range of histological features. Although germinomas have a generally better prognosis than most nongerminomatous tumors, they can have severe or even life-threatening presentations. Adipsic diabetes insipidus is one such severe presentation and its rarity can make it difficult to recognize and manage. Awareness of this potential entity is therefore important for clinical practice., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Testing for antinuclear antibodies is the most frequently prescribed analysis for the diagnosis of rheumatic diseases. Indirect immunofluorescence remains the gold standard method for their detection despite the increasing use of alternative techniques. In order to standardize the manual microscopy reading, automated acquisition and interpretation systems have emerged. This publication enables us to present our method of interpretation and characterization of antinuclear antibodies based on a cascade of analyses and to share our everyday experience of the G Sight from Menarini. The positive/negative discrimination on Hep cells 2000 is correct in 85% of the cases. In most of the false negative results, it is a question of aspecific or low titers patterns, but a few cases of SSA speckled patterns of low titers demonstrated a probability index below 8. Regarding the pattern recognition, some types and mixed patterns are not properly recognized. Concerning the probability index correlated in some studies to final titer, the weak fluorescence of certain patterns and the random presence of artifacts that distort the index don't lead us to continue it in our daily practice. In conclusion, automated reading systems facilitate the reporting of results and traceability of patterns but still require the expertise of a laboratory technologist for positive/negative discrimination and for pattern recognition.

Osteoarthritis (OA) is associated with a local inflammatory process. Dyslipidemia is known to be an underlying cause for the development of OA. Therefore, lipid and inflammatory levels were quantified ex vivo in blood and synovial fluid of OA patients (n=29) and compared to those of rheumatoid arthritis (RA) patients (n=27) or healthy volunteers (HV) (n=35). The role of apolipoprotein A-I (ApoA1) was investigated in vitro on inflammatory parameters using human joint cells isolated from cartilage and synovial membrane obtained from OA patients after joint replacement. Cells were stimulated with ApoA1 in the presence or not of serum amyloid A (SAA) protein and/or lipoproteins (LDL and HDL) at physiological concentration observed in OA synovial fluid. In our ex vivo study, ApoA1, LDL-C and total cholesterol levels were strongly correlated to each other inside the OA joint cavity whereas same levels were not or weakly correlated to their corresponding serum levels. In OA synovial fluid, ApoA1 was not as strongly correlated to HDL as observed in OA serum or in RA synovial fluid, suggesting a dissociative level between ApoA1 and HDL in OA synovial fluid. In vitro, ApoA1 induced IL-6, MMP-1 and MMP-3 expression by primary chondrocytes and fibroblast-like synoviocytes through TLR4 receptor. HDL and LDL attenuated joint inflammatory response induced by ApoA1 and SAA in a ratio dependent manner. In conclusion, a dysregulated lipidic profile in the synovial fluid of OA patients was observed and was correlated with inflammatory parameters in the OA joint cavity. Pro-inflammatory properties of ApoA1 were confirmed in vitro.

Determining the level of glycated haemoglobin, in particular its major fraction called HbA(1c), is an attractive tool in the management of diabetic patients. In fact, it provides a global evaluation of the glycemic control's level through the past 8-12 weeks. However, this tool must be used with caution. First of all, it does not allow to examine the glycemic kinetics since it represents a glycemic average. Secondly, it does not allow to appreciate the glycemic evolution through the full day. This dosage needs then sometimes to be complemented by fingersticks blood glucose testing. Last but not least, caution is advised in interpreting the results because a number of physiological, pathological and technical factors might interfere with HbA(1c) measurement. It is therefore important that physicians keep a critical view of the values obtained. The paper reviews the different methods used to determine the level of glycated haemoglobin and their limitations. It also emphasizes the medical situations in which over- and under-estimation of the real HbA(1c) value could occur. It does not address the specific issue of the new expression values of HbA(1c) in mmol/mol instead of %. Moreover, the medical situations in which over- and underestimation of the real HbA(1c) value could occur will be described.