To evaluate the possibility of an interfering factor in the immunoassays, we studied the same sample divided in 3 aliquots that were analyzed by three different laboratories using different techniques (Table 1): ELISA (DRG PSA equimolar, DRG International Inc

To evaluate the possibility of an interfering factor in the immunoassays, we studied the same sample divided in 3 aliquots that were analyzed by three different laboratories using different techniques (Table 1): ELISA (DRG PSA equimolar, DRG International Inc., Springfield, NJ, USA; PSA values were 110.3 ng/mL and 114.1 ng/mL), immunochromatography (VEDALAB PSA-CHECK, VEDALAB, Alencon, France; PSA values were 115.7 ng/mL and 98.7 ng/mL), and chemiluminescence (MAGLUMI Total PSA, Snibe Diagnostic, Shenzhen, China; PSA values were 0.8 ng/mL and 0.9 ng/mL). Table 1 Results of the values of PSA in three differents laboratories (A, B, and C) using enzyme-linked immunosorbent assay (ELISA), immunochromatography (IC), and chemiluminescence (CHL) techniques diagnostic tests, or immunoglobin therapy) [3]. 40% of clinical samples [2]. In many cases, these antibodies have nonspecific affinities and do not interfere with different immunoassays. However, for reasons not well understood, they can cause false-positive results in the analysis of different markers, even in the absence of antigen. Interference by HA is described in the analysis of different tumor markers (e.g., prostate-specific antigen [PSA], human chorionic gonadotropin, alpha-fetoprotein, cancer antigen 125, and calcitonin), infectious diseases, hormones, drugs, and cardiac markers (e.g., troponin-I) [3,4,5,6,7,8,9,10]. In this report, we describe an unusual case of a repeated spurious elevation of PSA possibly caused by HA. CASE REPORT A 52-year-old man presented with repeated elevation of PSA serum values (initial value, 19.7 ng/mL). During 2 years, the patient had a progressive increase in PSA levels reaching 108.7 ng/mL (PSA doubling time, 9.8 months; PSA velocity, 3.6 ng/mL/mo; Fig. 1). Controls were performed every 6 months with PSA. All analyses were performed by enzyme-linked immunosorbent assay (ELISA). The results of a digital rectal examination were not suspicious for prostate cancer and the results of three transrectal ultrasound-guided biopsies performed were all negative. Moreover, abdominal computed tomography and bone scans did not show any extraprostatic disease. Subsequently, a new serum test was performed in another laboratory using a chemiluminescent enzyme immunoassay (CHL). Contrary to the previous analysis, the new recorded PSA value was 1.02 ng/mL. This number was confirmed by a second determination. Open in a separate window Fig. 1 Evolution of prostate-specific antigen (PSA) values. As a result of the discrepancy in values, a false-positive result of the initial PSA tests was suspected. To evaluate the possibility of an interfering factor in the immunoassays, we studied the same sample divided in 3 aliquots that were analyzed by three different laboratories using different techniques (Table 1): ELISA (DRG PSA equimolar, DRG International Inc., Springfield, NJ, USA; PSA values were 110.3 ng/mL and 114.1 ng/mL), immunochromatography (VEDALAB PSA-CHECK, VEDALAB, Alencon, France; PSA values were 115.7 ng/mL and 98.7 ng/mL), and chemiluminescence (MAGLUMI Total PSA, Snibe Diagnostic, Shenzhen, China; PSA values were 0.8 ng/mL and 0.9 ng/mL). Table 1 Results of the values of PSA in three differents laboratories (A, B, and C) using enzyme-linked immunosorbent assay (ELISA), immunochromatography (IC), and chemiluminescence (CHL) techniques diagnostic tests, or immunoglobin therapy) [3]. T-26c Within specific antianimal antibodies, there exist different types: HAMA, human antirabbit antibodies, and human antigoat antibodies. RF is an auto-antibody that can also have HAMA-like activity, but its concentration in plasma is not high enough to cause significant interference [1]. Levinson and Miller [1] reported that HA interference in a healthy population is mainly due to natural polyspecific and idiotypic antibodies. By contrast, in allergic or diseased patients, the auto-antibody-type polyspecific or RF may be found more frequently. The prevalence of spurious elevated PSA values is around 0.3%. There are eight cases in the medical literature of falsely elevated PSA due to HA. Six of these patients were diagnosed with prostate cancer and continued to have detectable false Rabbit polyclonal to ADAMTS3 values of PSA after radical prostatectomy [6,7,8,9,10]. In some of these patients, an unnecessary salvage treatment was performed [6,8,9]. In the other two patients, the interference was detected during the screening [4,5], presenting with significantly high PSA values (up to 83 ng/mL), but only one patient did not receive an unnecessary therapeutic treatment [4]. In this case, we employed three “sandwich” immunoassays. These techniques use two monoclonal anti-PSA antibodies: a capture antibody (immobilized on a solid phase) and a detector antibody coupled to a signal transducer, such as an enzyme (ELISA) or a CHL. In ELISA, the enzyme substrate is added to produce a visible color. The intensity of the color produced is measured by spectrophotometry and indicates the amount of PSA in the sample. In CHL, there is an emission of light T-26c as the result of a chemical reaction and this intensity is also measured. The presence of HA links capture and detector antibodies in the absence of the antigen, creating a test interference and T-26c a false-positive result. The use of blocking agents could prevent this crosslink. The CHL technique is faster, is less expensive, and has higher sensitivity than ELISA. It may be more accurate at detecting false-positive results of elevated PSA due T-26c to HA, as was observed in the patient reported previously. Further studies would be required to support this assumption. HA represents a challenge for the laboratory analytical staff and remains an unpredictable problem. Different options can be considered to solve the HA interference. The simplest approach is to analyze the sample in another laboratory using a different formulation [1]. Another.