Prognostic role of carcinoembryonic antigen and carbohydrate antigen 19-9 in metastatic colorectal cancer: a BRAF-mutant subset with high CA 19-9 level and poor outcome.

BACKGROUND: Mutation status of RAS and BRAF, as well as serum levels of carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9), are biomarkers used in clinical management of patients with gastrointestinal cancers. This study aimed to examine the prognostic role of these biomarkers in a patient population that started first-line chemotherapy for unresectable metastatic colorectal cancer (mCRC) in the NORDIC-VII study. METHODS: CEA and CA 19-9 were measured in serum samples from 545 patients obtained before the start of chemotherapy. Four hundred and ninety-four patients had detectable levels of carbohydrate antigen 19-9 (CA 19-9). RAS (exons 2-4) and BRAF (V600E) mutation status were available from 440 patients. Overall survival (OS) was estimated in patient groups defined by serum CEA or CA 19-9 levels using cut-off values of 5 µg/L and 35 kU/L, respectively, in the total population and in subgroups according to RAS and BRAF mutation status. RESULTS: For both CEA and CA 19-9, elevated serum levels were associated with reduced OS in adjusted analyses which included RAS and BRAF mutation status, baseline World Health Organization performance status, and levels of alkaline phosphatase and C-reactive protein. The negative prognostic information provided by an elevated CA 19-9 level was particularly marked in patients with BRAF mutation (hazard ratio = 4.35, interaction P = 0.003, in an adjusted model for OS). CONCLUSIONS: High baseline serum concentrations of CEA and CA 19-9 provide independent information of impaired prognosis in mCRC. In patients with BRAF-mutant tumours, elevated serum CA 19-9 may identify a subgroup with highly aggressive disease and could contribute to improving therapeutic decisions.

Lowered reference limits for hCG improve follow-up of patients with hCG-producing tumors.

BACKGROUND: Human Chorionic Gonadotropin (hCG) is produced by germ cell tumors, but can also be elevated in benign conditions such as primary hypogonadism, where hCG is produced by the pituitary gland. In our experience, the reference limits for hCG (Elecsys hCG+ß-assay, Roche Diagnostics), were unnecessarily high and did not reflect levels encountered in clinical practice. We wanted to establish new reference limits to increase the clinical utility of the hCG-assay. METHODS: We analysed hCG in serum samples from a healthy adult population and in a cohort of testicular cancer survivors. The gonadotropins LH and FSH were measured in the cohort and in a selection of the reference population to assess gonadal function. RESULTS: We found low hCG levels for all men and women <45years (97.5 percentiles 0.1 and 0.2IU/L, respectively) from the healthy population (n=795) having normal FSH and LH. Due to assay limitations, we suggest a common reference limit of <0.3IU/L. For the age group ≥45, the 97.5 percentiles in the healthy population were 0.5IU/L for men and 6.0IU/L for women. In all subjects from both the reference population and the cohort (n=732), hCG levels exceeding the reference limit could be fully explained by reduced gonadal function indicated by elevated LH and FSH levels. CONCLUSION: The Elecsys hCG+ß-assay should have lower reference limits than recommended by the manufacturer, with important implications for tumor follow-up. Elevated hCG is rare with intact gonadal function, both in a normal population and among survivors of testicular cancer, and should lead to further investigations when encountered in clinical practice.

HE4 as an Early Detection Biomarker of Epithelial Ovarian Cancer: Investigations in Prediagnostic Specimens From the Janus Serumbank.

OBJECTIVES: Epithelial ovarian cancer is characterized by nonspecific signs and clinical symptoms arising at late stages. Early detection is therefore important and may significantly improve the survival rate. Cancer antigen 125 (CA125) has been the most extensively studied serum biomarker in epithelial ovarian cancer, but low specificity limits its usefulness. A relatively novel biomarker, human epididymis protein 4 (HE4), has shown promise in early detection of the disease. The aim of this study was to investigate how early the tumor marker increases before diagnosis. METHODS/MATERIALS: A nested case-control design was used to evaluate the performance of HE4 and CA125 in prediagnostic serum samples from the Janus Serumbank. Serial specimens from 120 women with invasive epithelial ovarian cancer were compared with healthy controls. Serum level of CA125, HE4, and cotinine was measured. Spearman correlation and multiple linear regression analyses were used to investigate impact of smoking, age, storage time, and lag time (time from sampling until date of diagnosis). RESULTS: Spearman correlation showed a strong positive correlation between HE4 and smoking in both cases and controls. Multiple linear regression analyses for pairwise differences between case and control showed that serum level of HE4 and CA125 was significantly increased (P = 0.002 and P < 0.001, respectively) 2 years before diagnosis and that CA125 also was significantly increased up to 4 years before diagnosis (P = 0.002). CONCLUSIONS: The present study showed that a difference between cases and controls in serum concentration of HE4 seemed to be increased 2 years before diagnosis and that CA125 was increased until 4 years before diagnosis.

Heterophilic antibody interference in immunometric assays.

Immunometric assays are inherently vulnerable to interference from heterophilic antibodies, endogenous antibodies that bind assay antibodies. The consequences of such interference can be devastating. In this review, we discuss strategies that reduce the damage caused by heterophilic antibodies. Clinicians should only order blood tests that are indicated for the patient and clinical setting at hand, and have the confidence to question laboratory results discordant with the clinical picture. Laboratorians should familiarize themselves with the vulnerability of the assays they offer, and be able to perform and interpret adequate confirmatory measures correctly. When designing immunoassays, the immunoassay industry should invest the necessary resources in specific protective measures against heterophilic antibody interference. Examples include using antibody fragments and the addition of effective blockers to assay reagents. The increasing use of modified monoclonal mouse antibodies both in therapy and diagnostics could present a particular challenge in the future.

Human epididymis protein 4 reference limits and natural variation in a Nordic reference population.

The objectives of this study are to establish reference limits for human epididymis protein 4, HE4, and investigate factors influencing HE4 levels in healthy subjects. HE4 was measured in 1,591 samples from the Nordic Reference Interval Project Bio-bank and Database biobank, using the manual HE4 EIA (Fujirebio) for 802 samples and the Architect HE4 (Abbott) for 792 samples. Reference limits were calculated using the statistical software R. The influence of donor characteristics such as age, sex, body mass index, smoking habits, and creatinine on HE4 levels was investigated using a multivariate model. The study showed that age is the main determinant of HE4 in healthy subjects, corresponding to 2% higher HE4 levels at 30 years (compared to 20 years), 9% at 40 years, 20% at 50 years, 37% at 60 years, 63% at 70 years, and 101% at 80 years. HE4 levels are 29% higher in smokers than in nonsmokers. In conclusion, HE4 levels in healthy subjects are associated with age and smoking status. Age-dependent reference limits are suggested.

Heterophilic antibody interference in commercial immunoassays; a screening study using paired native and pre-blocked sera.

BACKGROUND: Heterophilic antibodies are still an important source of interference in immunoassays. We have conducted a screening study for interference in a panel of commercially available assays using two sera known to contain high titer Fc-reactive heterophilic antibodies. METHODS: The sera were distributed to laboratories participating in the Nordic External Quality Assessment cooperation (EQANord). Duplicate samples pre-blocked with aggregated murine monoclonal MAK33 were also supplied. Discrepancies (>50%) between the results for native and blocked samples were used to classify the tested assays as susceptible to interference. A total of 170 different assay kits covering 91 analytes were tested. RESULTS: We found that 21 assays, covering 19 different analytes, were susceptible to interference from the heterophilic antibodies in the two sera. Many of these are clinically and commercially important assays. Some of the false results were grossly elevated and could have been detrimental to patient care in a clinical setting. CONCLUSIONS: Heterophilic antibodies with Fc-reactivity remain a threat. A more widespread use of antibody fragments and aggregated immunoglobulin could potentially improve the heterophilic antibody resistance of assays intended for clinical use.

Splenic marginal zone lymphoma with VH1-02 gene rearrangement expresses poly- and self-reactive antibodies with similar reactivity.

One-third of all splenic marginal zone lymphomas (SMZL) use the IgH VH1-02 gene. These cases are usually not associated with hepatitis C virus infection. Of interest, the rearranged VH1-02 genes display similar complementarity determining regions 3, a finding confirmed by our study. The latter suggests that these SMZL may produce antibodies with similar reactivity. We produced recombinant antibodies from 5 SMZL cases with VH1-02 gene rearrangement to study the binding reactivity of these antibodies. Surprisingly, the recombinant antibodies demonstrated poly- and self-reactivity as demonstrated by their reactivity with nuclear, cytoplasmic, as well as membranous antigens expressed by human cells and by reactivity with human serum. This polyreactivity was specific as demonstrated by ELISA. The antibodies did not react with proteins on the cell surface that are induced by apoptosis as shown for antibodies produced by chronic lymphatic leukemia with VH1-02 gene rearrangement. The results indicate that a common subset of SMZL arises from polyreactive B cells, a subset of marginal zone B cells that are important in the immunologic defense against infection.

Differences in total human chorionic gonadotropin immunoassay analytical specificity and ability to measure human chorionic gonadotropin in gestational trophoblastic disease and germ cell tumors.

OBJECTIVE: To determine the ability of several radioimmunoassays and commercial two-site immunoassays to detect the first World Health Organization International Reference Reagents (IRRs) for 6 defined human chorionic gonadotropin (hCG) variants and to compare their performance in measuring hCG in sera from patients with gestational trophoblastic disease (GTD) and germ cell tumors (GCTs) of the testis or ovary. STUDY DESIGN: The reactivity of the different assays with the 6 IRRs together with the current fourth International Standard (IS, 75/589) was tested using 5 commercial two-site assays as well as 2 competitive polyclonal radioimmunoassays (RIAs) and a competitive monoclonal immunoassay. Individual samples from 41 patients (19 GCT and 22 GTD) with high circulating levels of hCG (range, 718-6,055,000 IU/L) were diluted and measured using the various immunoassays. RESULTS: The results of 4 GCT patient samples varied markedly among the assays, including 1 sample that was grossly underestimated by 3 of the commercial assays. CONCLUSION: Comparison of each assay's reactivity to the variant isoforms revealed that recognition of the isoforms was highly variable, particularly for hCGbeta and hCGbeta core fragment (hCGbetacf).

Exploring the complementary selectivity of immunocapture and MS detection for the differentiation between hCG isoforms in clinically relevant samples.

Whereas numerous immunoassays have been developed to ensure detection of the entire spectrum of isoforms displayed by the human chorionic gonadotropin (hCG) molecule, significant variation has been demonstrated in how these isoforms are recognized by the antibodies in different immunoassays. The aim of this study was to establish a method using the dual selectivity of the immunoextraction and the mass spectrometry detection for the differentiation between various hCG isoforms in clinically relevant samples. Immunoextraction of endogenous hCG isoforms using a monoclonal antibody (E27) on a 96-well microtitier plate, followed by in-well tryptic digestion, and SIM monitoring of the selected signature peptides, resulted in the qualitative differentiation between several hCG isoforms in serum or urine. We conclude that the orthogonal selectivity conferred by the combination of immunoaffinity extraction and LC-MS analysis offers valuable complementary information to the conventional immunoassays.