Band 47, Heft 10

The increased analytical sensitivity of the new generation of methods for cardiac troponin I (cTnI) and T (cTnT) has demonstrated that measurable troponin is present in the blood of healthy adult subjects. These data are not in accordance with the prevailing opinion that any reliably detected increase in cardiac troponins should be considered abnormal and potentially caused by cardiac necrosis. The goal of the present review is to discuss the hypothesis that cardiac troponins can be released from cardiomyocytes, even in healthy adult subjects as a result of a process related to “physiological renewal” of the human myocardium and possibly enhanced by physical exercise or aging. The latest generation of high-sensitive cTnI and cTnT immunoassays are characterized by detection limits (DLs) as low as a few picograms. This clearly represents a greater increase in discrimination than that obtained by the most sophisticated cardiac imaging techniques that are commercially available at present. However, the critical question is whether high-sensitive troponin assays are clinically useful and in particular, whether some specific laboratory biomarkers (such as cTnI and cTnT) yield better diagnostic (or prognostic) accuracy and cost-effectiveness when compared with echocardiography in patients with cardiovascular disease. Only specific and well-designed clinical trials will answer this important question. Clin Chem Lab Med 2009;47:1167–77.

The recently released document by the Global Task Force on the “universal” definition of myocardial infarction (MI) recommends a single decision limit for cardiac troponin (cTn) corresponding to the 99th percentile limit of the reference value distribution [99th upper reference limit (URL)] for the diagnosis of patients presenting with suspected MI. However, use of this cut-off concentration posed a problem because most assays do not have the sensitivity to consistently measure cTn in the blood of apparently healthy individuals, with a high proportion of the values being below the method's detection limit. In addition to the influence of assay sensitivity, the 99th URL for cTn can vary depending on the reference population used, and its sample size. A marked difference can also be observed between the 99th URL obtained using plasma vs. that obtained with serum. Finally, some interferences with cTn measurement (e.g., by heterophile antibodies) may become more noticeable using assays that have increased analytical sensitivity that measure lower concentrations of these markers. In conclusion, a number of issues can markedly influence the definition of the 99th URL for cTn, which most clinicians are unaware of and may markedly condition the clinical performance of the test in routine practice. Clin Chem Lab Med 2009;47:1179–82.

The contractile sarcomeric pool of skeletal muscle and heart consists of a highly-ordered arrangement of actin thin filaments, tropomyosin and proteins of the troponin complex: troponin I (TnI), troponin T (TnT) and troponin C (TnC). The cardiac myocyte expresses specific isoforms of both TnI and TnT (cTnI and cTnT, respectively), which can be distinguished from skeletal muscle isoforms by rapid and reliable immunoassays. Due to their superior cardiac specificity, cTnI and cTnT have become the recommended biomarkers for the diagnosis of myocardial injury. The most common applications are for risk stratification and diagnosis of acute coronary syndromes, albeit they can also be used for assessing a variety of other myocardial disorders. However, the excellent diagnostic efficiency of cardiac troponin testing is jeopardized by some pre-analytical issues (unsuitable specimens for testing, analyte stability, handling, transportation and storage of specimens prior to analysis), as well as by analytical concerns related to standardization or harmonization of cTnI immunoassays, imprecision at low concentrations, antibody specificity, immunoreactivity of plasma isoforms released in the blood after myocardial injury, interference from autoantibodies, heterophilic antibodies, rheumatoid factor, and human anti-mouse antibodies. In addition, although the influence of some known mutations in cTnT and cTnI on calcium sensitivity and force generation have been readily demonstrated, their influence on current immunoassays is unknown. Most mutations in these proteins may contribute to the development of certain cardiomyopathies, namely hypertrophic and restrictive. In these situations, the phenotype is characterized by the underlying diseases, and the ability to detect cTnT or cTnI is of relatively little clinical significance. However, the cTnT Arg129Lys polymorphism and those observed in the stable domain of cTnI do not significantly alter the functional properties of the molecule within the myocardium and thus are predictably asymptomatic. While the actual prevalence of these polymorphisms in the general population is still unknown, they might be a source of potential analytical problems; modifying the immunogenicity of the molecule and leading to potential false negative results. The goal of this article is to provide an overview on the potential technical and analytical challenges in the measurement of cardiac troponins, along with the significance of polymorphisms in the genes encoding for cTnI and cTnT in both health and disease. Clin Chem Lab Med 2009;47:1183–94.

To face the economic pressures arising from the current socio-economic conjuncture, hospital laboratories are endangered by an increasing trend towards the outsourcing of clinical laboratory tests to external (mega-) laboratories. This should allow hospitals to meet their economic requirements, but with an increased risk of loss of medical quality and, mid- to long-term, loss of cost effectiveness of healthcare at the national level. To anticipate current developments (economical and technological) that inevitably will affect the future of laboratory medicine, hospital laboratories should be proactive and enhance efficiency, reduce costs by consolidation, integrate into regional networks, and form alliances or partnerships. To create additional value, the core competency of laboratory professionals must be refocused to provide medical knowledge services (consultative support to clinicians) related to in vitro diagnostic testing. To integrate cost-efficiency with medical quality, implementation of a matricial organization – operational vs. biomedical level – could be an interesting approach. This integrated structure should create total quality of laboratory testing, managing the entire medical diagnostic cycle from the pre-preanalytical to post-postanalytical phase. Clin Chem Lab Med 2009;47:1195–201.

Laboratory results are reported in different units (despite international recommendations for SI units) together with different reference limits, of which several exist for many quantities. It is proposed to adopt the concept of the intelligence quotient and to report quantitative results as a quantity quotient (QQ) in laboratory medicine. This quotient is essentially the difference (measured result minus mean or mode value of the reference interval) divided by the observed biological variation CV o . Thus, all quantities are reported in the same unit system with the same reference limits (for convenience shifted to e.g., 80–120). The critical difference can also be included in this standardization concept. In this way the information of reference intervals and the original result are integrated into one combined value, which has the same format for all quantities suited for quotient reporting (QR). The proposal of QR does not interfere with neither the current concepts of traceability, SI units or method standardization. This proposal represents a further step towards harmonization of reporting. It provides simple values which can be interpreted easily by physicians and their patients. Clin Chem Lab Med 2009;47:1203–6.

Over the past decade, research in Biochemistry and Molecular Biology has developed rapidly worldwide. The present study was designed to study the characteristics of publications in Biochemistry and Molecular Biology journals between 1999 and 2008 from the six top-ranking countries – the United States (USA), Japan, Germany, United Kingdom (UK), China and France. We also examined the research output from three different regions – Mainland China (ML), Hong Kong (HK) and Taiwan (TW). The USA contributed 34.1% of the world's total output and ranked first, but its percentage of research articles in this field went down. In total, 26,867 articles were published in journals with an impact factor (IF) <10.000, and 46.5% of these were from the USA. China contributed 4.2% of the total in 268 journals, 0.5% of which were journals with the top 10 IF. Our analysis describes the output from each country and region, and reveals the positive trend in China during the period of 1999–2008. In contrast to other countries, our results suggest that China is behind in conducting high-quality research. Clin Chem Lab Med 2009;47:1211–6.

Background: The poor response to antiviral treatment of hepatitis C virus (HCV)-infected patients with genotype 1b has been associated with a higher prevalence of metabolic syndrome. However, the molecular link between these clinical entities is not clear. The goal of this study was to clarify the role of genotype 1b and 2 in the genetic expression of suppressor of cytokine signaling 3 (SOCS3) and insulin receptor substrate 1 (IRS-1). Methods: We infected human hepatocellular carcinoma cell line (HepG2) cells with human HCV genotype 1b or 2 and measured the gene and protein expression of SOCS3 at various times. We also evaluated impairment in the insulin pathway by analysis of IRS-1 and phospho-AKT. For the control, we used HepG2 cell cultures treated with non-infectious serum. We also demonstrated the occurrence of HCV infection by the detection of both positive and negative strands in the cells and culture medium. To test infection of the HepG2 cells, we performed quantitative real-time polymerase chain reaction (qRT-PCR) of viral load at different time points. We analyzed the viral genotype in the pellet and supernatant. Results: At each time point, we found positive and negative strands in the infected cells, while in the medium we found positive, but no negative strands. We also detected the presence of the correct genotype in the medium. Two weeks following infection when the viral load was higher, we tested genotype 1b and 2 infected cells. SOCS3 gene expression was significantly higher in genotype 1b-infected cells (median 2.56; mean 2.82±0.59) compared with genotype 2 (median 1.34; mean 1.46±0.31) (p=0.04) and control cells (median 1.09; mean 1.02±0.11, p=0.02). There was no difference between cells exposed to genotype 2 and control cells. Conversely, IRS-1 was significantly lower in genotype 1b-infected cells (median 15.97; mean 15.45±0.67) compared with genotype 2-infected cells (median 16.45; mean 16.44±0.01, p=0.04). Statistically significant differences were seen when comparing the pAKT/AKT ratio in genotype 1b-infected cells (0.19±0.034) and not genotype 1b-infected (genotype 2-infected and non-infected) cells (0.253±0.004, p=0.03). This inverse regulation is compatible with interactions between the molecular expression of SOCS3, IRS-1 and phospho-AKT mediated by the genotype 1b virus. Conclusions: Up-regulation of the SOCS3 gene might be one of the mechanisms governing non-response to therapy and expression of insulin resistance mediated via a direct mechanism at this level of genotype 1b HCV. Clin Chem Lab Med 2009;47:1217–25.

Background: The β1-adrenergic receptor (ADRB1) plays a pivotal role in mediating signal transduction of the sympathetic-adrenal system, which is involved in the regulation of cardiac output and peripheral resistance. Our goal was to determine whether the polymorphisms Arg389Gly (rs1801253) and Ser49Gly (rs1801252) of the ADRB1 gene were associated with essential hypertension in Chinese. Methods: We tested our hypothesis in two independent case-control studies, one comprised 481 patients with hypertension and 529 control subjects, and the other study comprised 212 patients and 325 control subjects. All subjects were genotyped for Arg389Gly and Ser49Gly polymorphisms. Results: The first study showed that the Arg389Arg genotype of the ADRB1 gene was associated with risk of hypertension [odds ratio (OR) 1.77, 95% confidence interval (CI) 1.09–2.98; p=0.008], and the association was replicated in the second independent population (OR 1.65, 95% CI 1.07–2.89, p=0.01). The patients with the Arg389Arg genotype had significantly higher diastolic blood pressure (DBP) than did those with Arg389Gly genotype as well as those with Gly389Gly genotype (100.29±11.01 mm Hg vs. 95.33±13.10 mm Hg and vs. 96.17±12.18 mm Hg, respectively, p=0.01, p=0.02). The association was replicated in the second study (103.7±13.3 mm Hg vs. 97.31±12.9 mm Hg and vs. 96.29±13.4 mm Hg, respectively, p=0.03, p=0.02). Heart rate also showed an association (in first study: 79.43±9.90 bpm vs. 74.87±8.96 bpm, vs. 73.92±8.18 bpm, respectively, p=0.02, p=0.014; in the second study: 81.12±8.99 bpm vs. 74.85±7.97 bpm and vs. 73.89±9.12 bpm, p=0.007, p=0.006, respectively). No association was seen between systolic blood pressure (SBP) and any of the three genotypes at amino acid position 389 in hypertensive patients, neither between the Ser49Gly polymorphisms and hypertension, nor between the Ser49Gly genotypes and DBP and heart rate. Conclusions: The polymorphisms of the ADRB1 gene were associated with essential hypertension. The Arg389Gly polymorphism of the ADRB1 gene confers higher risk for hypertension. Clin Chem Lab Med 2009;47:1227–31.

Background: Glycogen storage disease type III (GSD III) is caused by mutations in AGL which encodes for a single protein with two enzyme activities: oligo-1, 4-1, 4-glucantransferase (transferase) and amylo-1, 6-glucosidase. Activity of both enzymes is lost in most patients with GSD III, but in the very rare subtype IIId, transferase activity is deficient. Since the spectrum of AGL mutations is dependent on the ethnic group, we investigated the clinical and molecular characteristics in Egyptian patients with GSD III. Methods: Clinical features were examined in five Egyptian patients. AGL was sequenced and AGL haplotypes were determined. Results: Six novel AGL mutations were identified: a large deletion (c.3481–3588+1417del1525 bp), two insertions (c.1389insG and c.2368insA), two small deletions (c.2223–2224delGT and c.4041delT), and a missense mutation (p.L620P). p.L620P was found in a patient with IIId. Each mutation was located on a different AGL haplotype. Conclusions: Our results suggest that there is allelic and phenotypic heterogeneity of GSD III in Egypt. This is the second description of a large deletion in AGL . p.L620P is the second mutation found in GSD IIId. Clin Chem Lab Med 2009;47:1233–8.

Background : High-density lipoprotein (HDL) is a major plasma lipoprotein directly associated with cholesterol metabolism. The ATP binding cassette transporter 1 gene ( ABCA1 ) is one of the major genes modulating plasma levels of HDL-cholesterol (HDL-C). Rare alleles of ABCA1 associated with extreme HDL-C concentrations have not been previously investigated in the Chinese. Methods : Blood samples were collected from 470 subjects whose HDL-C concentrations were within the top 5% of the distribution, 335 subjects in the lowest 5%, and 220 within the range 5%–95%. First, we sequenced all exons of the ABCA1 gene from 50 subjects from the group with extremely high HDL-C, and 50 from the group with extremely low HDL-C concentrations. Next, in the remaining subjects, we genotyped the non-synonymous variants identified exclusively with either extreme group. Results : Four novel non-synonymous alleles were identified; all were rare. Alleles c.3029C>T (p.Ala1010Val) and c.5399A>G (p.Asn1800Ser) were found exclusively in the low group, c.2031C>A (p.Asp677Glu) and c.2660G>T (p.Cys887Phe) exclusively in the high group. Conclusions : Our results show that some rare alleles of ABCA1 are associated with marked phenotypes, supporting the “rare-variant common-disease” hypothesis. Certain alleles also provide tools for identifying individuals at high risk of dyslipidaemia, allowing for early therapeutic intervention. Clin Chem Lab Med 2009;47:1239–45.

Background: Recent research has shown that inflammation plays a key role in coronary artery disease (CAD) and other manifestations of atherosclerosis. Several lines of evidence support a key role for tumor necrosis factor-α (TNF-α), a potent immunomodulator and pro-inflammatory cytokine, in the development of atherosclerosis and in complications of CAD. Methods: We investigated the possible association between CAD and the TNF gene promoter polymorphisms –308G>A and –1031T>C in a Tunisian population. We compared the distribution of these polymorphisms between 418 patients with CAD and 406 healthy controls using polymerase chain reaction restriction fragment length-polymorphism analysis. Results: The frequency of the TNF-α –308A allele in the control group was similar to that observed in CAD patients [p=0.78; odds ratio (OR)=1.15; 95% confidence interval (CI)=0.86–1.55], but higher than those described in other Europeans, such as in the French, Finnish and Spanish. Concerning the TNF-α –1031T/C polymorphism, the same distribution was observed between patients with CAD and controls (p = 0.12; OR=1.27; 95% CI=0.94–1.72). In addition, the genotype and allele frequencies of control individuals were comparable to those previously reported in healthy Tunisian controls and other ethnic groups. Haplotype analysis (TNF-α –308G>A and –1031T>C) demonstrated no significant association between TNF haplotypes and CAD. Conclusions: We conclude that TNF promoter gene polymorphisms at position –308G>A and –1031T>C do not play a major role in the pathogenesis of CAD in the Tunisian population. Clin Chem Lab Med 2009;47:1247–51.

Background : We report our results for the systematic recording of all errors in a standard clinical laboratory over a 1-year period. Methods : Recording was performed using a commercial database program. All individuals in the laboratory were allowed to report errors. The testing processes were classified according to function, and errors were classified as pre-analytical, analytical, post-analytical, or service-related, and then further divided into descriptive subgroups. Samples were taken from hospital wards (38.6%), outpatient clinics (25.7%), general practitioners (29.4%), and other hospitals. Results : A total of 1189 errors were reported in 1151 reports during the first year, corresponding to an error rate of 1 error for every 142 patients, or 1 per 1223 tests. The majority of events were due to human errors (82.6%), and only a few (4.3%) were the result of technical errors. Most of the errors (81%) were pre-analytical. Of the remainder, 10% were analytical, 8% were post-analytical, and 1% was service-related. Nearly half of the errors (n=550) occurred with samples received from general practitioners or clinical hospital wards. Identification errors were relatively common when non-technicians collected blood samples. Conclusions : Each clinical laboratory should record errors in a structured manner. A relation database is a useful tool for the recording and extraction of data, as the database can be structured to reflect the workflow at each individual laboratory. Clin Chem Lab Med 2009;47:1253–7.

Background: This study evaluates HbA1c measurements from dried blood spots collected on filter paper and compares HbA1c from filter paper (capillary blood) with HbA1c measured in venous blood. Methods: Patient satisfaction was evaluated using a questionnaire. The performance with the filter paper method was assessed by comparing HbA1c results from EDTA-blood samples obtained via dried blood spots with HbA1c results obtained with freshly hemolyzed blood (routine HbA1c). Adult patients visiting the outpatient clinic for HbA1c analyses were recruited for the evaluation of dried blood spot sampling at home. Laboratory personnel collected a capillary blood sample on filter paper as well as a venous EDTA-blood sample. The participants collected another capillary blood sample at home and sent the dried filter paper back to the laboratory. Samples were analyzed with an immunoturbidimetric assay. Results: Between-filter coefficient of variation was 1.8%. Filter paper HbA1c increased slightly during storage, particularly during the first 5 days. Filter paper HbA1c highly correlated with routine HbA1c (r=0.987). The evaluation of samples collected at home showed comparable HbA1c values by filter paper and routine sampling methods (n=93). Eighty-three percent of participants said they would like the filter method to be brought into practice. Conclusions: Home HbA1c sampling on filter paper is an acceptable sampling alternative for analysis of HbA1c. Clin Chem Lab Med 2009;47:1259–64.

Background: Endothelial cell antigens are important targets in acute rejection (AR). Our goal was to measure the serum concentrations of pre-transplant anti-endothelial cell antibody (AECA) in panel reactive antibody (PRA) negative recipients and its impact on AR within 6 months following renal transplantation. Methods: We retrospectively examined pre-transplant sera from 392 patients using cellular enzyme linked immunosorbent assay (ELISA) with substrate from a permanent endothelial cell line EAhy926 . Equal volumes of serum from 40 healthy volunteers were mixed and used as the negative control. Results: The positive rate of AECA was 15.8%. There were no significant differences with respect to age, gender, original disease, dialysis history, immune suppressive regimen, cytomegalovirus (CMV) antigen positive rate, complement dependent cytotoxicity (CDC) level and soluble CD30 (sCD30) levels between the AECA positive group and AECA negative group. AR rate in the AECA positive group was higher than that in the AECA negative group (35.5% vs. 22.4%, p=0.023). The AECA positive patients had significantly higher rates of acute grade II T-cell mediated rejection (TMR) and acute antibody mediated rejection (AMR) compared with AECA negative patients. The concentrations of sCD30, and AECA were independent risk factors for AR within 6 months; the odds ratios were 7.005 and 2.469, respectively. Conclusions: Positive AECA was an independent risk factor for AR and appeared to correlate with relatively severe rejection subtypes. Clin Chem Lab Med 2009;47:1265–9.

Background: Analysis of cerebrospinal fluid (CSF) to discriminate between benign and malignant conditions is of fundamental importance for the physician and the patient because of the differential therapeutic options and resulting morbidity and mortality. Most human tumours demonstrate increased telomerase activity (TA). Recent technical advances in the detection of TA allow for sensitive and specific detection within 4 h. Thus, the detection of TA is suitable for routine clinical testing. Methods: This study examines TA in cellular proteins in CSF from 111 patients compared to cytomorphological and laboratory examination. Results: A positive result for TA in cellular proteins of CSF was correlated significantly with Meningeosis neoplastica , but not with non-malignant conditions. Telomerase was not detected in CSF supernatant, despite positive results in cellular proteins from identical patients. Furthermore, a 48-h time delay during the pre-analytic processing is not critical for detection of TA detection in native CSF when stored at room temperature. Conclusions: We conclude that TA is a promising marker for the detection of Meningeosis neoplastica and warrants further study. Clin Chem Lab Med 2009;47:1271–6.

Background: The aim of this study was to determine whether haptoglobin (Hp) genotypes are associated with prognosis in patients with squamous cell carcinoma of the head and neck (HNSCC). Methods: We studied patients with HNSCC without distant metastasis at diagnosis. The Hp genotype of each patient was determined and the prognostic significance of the Hp genotype was further analyzed. Pearson's χ 2 -test or Fisher's exact test were used to analyze correlations between Hp genotype and clinical characteristics of HNSCC. Eighty patients with newly diagnosed HNSCC who were treated with curative modality were enrolled in this study. Kaplan-Meier plots and log-rank test were used to compare locoregional recurrence-free survival, distant-metastasis-free survival and overall survival of patients according to Hp genotype. Survival analysis was performed using Cox proportional hazard models. Results: Eighty patients with newly diagnosed HNSCC were enrolled in this study. There was no significant difference in the distribution of Hp genotypes in HNSCC patients and healthy individuals (p=0.959). Matched-pair analysis showed that locoregional recurrence-free survival was poor (p=0.02) for HNSCC patients with Hp 2-2 or 2-0. There was no significant difference in distant metastasis-free survival and overall survival (p=0.422 and 0.509, respectively). Multivariate analysis showed that Hp 2-2 or 2-0 was associated with an increased risk of locoregional recurrence [Hazard ratio (HR) 5.9; 95% confidence interval (CI), 1.1–6.65; p=0.038]. The risk was still higher in patients with Hp 2-2 or 2-0 after further adjusting for age and treatment modality (HR 7.6; 95% CI, 1.2–46; p=0.028) in locoregional recurrence-free survival. Conclusions: The present data show that the Hp genotype is closely related to recurrence rate in patients with HNSCC. Patients with Hp 2-2 or 2-0 have greater locoregional recurrence and significantly increased HRs in multivariate analysis. The Hp genotype may be a prognostic factor in patients with HNSCC. Clin Chem Lab Med 2009;47:1277–83.

Background: The measurement of serum thyroglobulin (Tg) is widely used as a marker for recurrence of thyroid carcinoma following total thyroidectomy. However, this method cannot differentiate between benign and malignant disease. We focused on the sugar chain in the Tg molecule and investigated the usefulness of Lens culinaris agglutinin (LCA)-reactive Tg ratios in sera and wash fluids obtained during fine-needle aspiration (FNA) for the detection of thyroid carcinoma. Methods: The study was performed using 203 serum samples (115 from patients with benign thyroid disease and 88 from patients with thyroid carcinomas) and 176 wash fluid samples (143 benign, 21 malignant, and 12 inconclusive). LCA-reactive Tg ratios were determined using an enzyme-linked immunosorbent assay, and a comparison was made between malignant and benign lesions. Results: In serum, the ratio in patients with malignancy was 79.5±6.0 [mean±standard deviation (SD)], significantly lower than in patients with benign lesions (84.9±3.5). The ratios in wash fluid from malignant lesions (75.8±18.9) were also significantly lower than those from benign lesions (85.6±3.9). Conclusions : These results suggest that this method could distinguish between benign and malignant lesions and may be useful for screening serum and wash samples. Clin Chem Lab Med 2009;47:1285–90.

Background : The soluble transferrin receptor (sTfR) is established as a test for iron deficiency (ID). In chronic lymphocytic leukemia (CLL), sTfR is not reliable for screening for ID as the latter is strongly dependent on tumor burden. Methods : We investigated whether the influence of the tumor load can be excluded or minimized using the sTfR/log ferritin ratio (TfR-F-Index) and the C-reactive protein (CRP)-adjusted TfR-F-Index in 87 patients with CLL. sTfR was measured nephelometrically (normal: 0.81–1.75 mg/L). A cut-off value of 1.5 for the TfR-F-Index and 0.8 for the CRP-adjusted TfR-F-Index, in patients with a CRP >5 mg/L, was used. Results : All Binet A patients had normal sTfR values (1.34±0.2 mg/L), TfR-F-Index (0.67±0.2) and a CRP-adjusted TfR-F-Index. In Binet B and C, sTfR and the TfR-F-Index were significantly increased compared to Binet A patients (p<0.0001). The differences between Binet B and C were not significant. sTfR was increased in 85%, TfR-F-Index in 46% and the CRP-adjusted TfR-F-Index in 54% of the Binet B patients, in Binet C patients, 80%, 50% and 60% showed increases, respectively. sTfR and the TfR-F-Index decreased or even normalized following successful treatment. Conclusions : Similar to sTfR, the TfR-F-Index is strongly associated with tumor burden in patients with CLL. Thus, these parameters do not allow for a reliable diagnosis of ID in this patient group. Clin Chem Lab Med 2009;47:1291–5.

Background: The clinical relevance of chromogranin A (CgA) concentrations depends on the analytical performance of the assay. The goal of the present study was to define the clinical involvements in CgA calibration models by evaluating the confidence intervals (CIs) for values from patients who were undergoing monitoring for disease. Methods: Thirty calibration curves for the CgA assay [immunoradiometric assay (IRMA), (CIS-BIO)] were built using linear regression (LR), and four-parameter logistic models were used to estimate CIs for patient concentrations. Results: We reported the inadequacy of the LR curve estimation procedure. We showed: 1) no evidence that the straight calibration line could fit the average responses, 2) non-constant and non-uniform variance of the replicated calibration responses. All tests performed in the analysis of variance and CI calculation for the calibration curve should be invalidated. The four-parameter logistic function yielded results for 16 curves only; this result could be due to the low number and inappropriate concentration of calibrators. This suggests that some aspects of the assay design should be reviewed. However, using the variance function estimated in this model, we could assess the CI for calibration curves and patient samples. Conclusions: We showed that the four-parameter logistic calibration model with estimated variance function should better support clinical interpretation of marker concentration changes in patients serially tested. Clin Chem Lab Med 2009;47:1297–303.