The measurement of free hemoglobin (free Hb) in blood is crucial for assessing the risk of organ damage in patients with hemolytic diseases. However, the colorimetric method, commonly used in clinical practice, does not distinguish between free Hb and the hemoglobin-haptoglobin complex (Hb-Hp) in the blood, instead reflecting the total Hb level. Although size-exclusion high-performance liquid chromatography (SEC-HPLC) can specifically measure free Hb, its clinical use is limited by long assay times. Here, we developed a novel assay method for the rapid quantification of free Hb in serum, distinguishing it from Hb-Hp, using a latex agglutination immunoturbidimetric assay (LATIA). This method could be used to measure free Hb in sera in the range of 1-100 μg/mL in approximately 15 min using an automatic biochemistry analyzer. Using Hb-spiked serum samples from healthy adults, there was a high correlation with Hb levels determined using the newly developed method and SEC-HPLC, indicating a high specificity for free Hb. This novel assay can be used to monitor levels of free Hb in patients with various hemolytic diseases and to design therapeutic strategies based on measured values. However, further studies are required to assess its clinical performance.

OBJECTIVE: Fecal calprotectin (Fcal) as well as the fecal immunochemical test (FIT) are useful biomarkers for detecting activity and mucosal healing in inflammatory bowel diseases. Here, we report the performance of simultaneous measurements of Fcal and FIT for ulcerative colitis (UC) patients using the newly-developed latex agglutination turbidimetric immunoassay (LATIA) system.
METHODS: Fcal and hemoglobin were measured by the LATIA system in 152 UC patients who underwent colonoscopy. Fcal was also quantified with a conventional enzyme-linked immunosorbent assay (ELISA). Fecal markers were evaluated in conjunction with the mucosal status of UC, which was assessed via the Mayo endoscopic subscore (MES) classification.
RESULTS: The LATIA system could quantify calprotectin and hemoglobin simultaneously with the same fecal samples within 10 minutes. The values of the Fcal-LATIA closely correlated with those of the Fcal-ELISA (Spearman rank correlation coefficient, r=0.84; P<0.0001). The values of Fcal for each assay and the FIT all significantly correlated with the MESs (Spearman rank correlation coefficient, Fcal-LATIA: r=0.58, Fcal-ELISA: r=0.55, and FIT: r=0.72). The mucosal healing predictability (determined by an MES of 0 alone) of the Fcal-LATIA, Fcal-ELISA, and FIT-LATIA with the cutoffs determined by receiver operating characteristic curve analysis was 0.79, 0.78, and 0.92 for sensitivity, respectively, and 0.78, 0.69, and 0.73 for specificity, respectively.
CONCLUSIONS: The performance of the novel Fcal-LATIA was equivalent to that of the conventional Fcal assay. Simultaneous measurements with FITs would promote the clinical relevance of fecal biomarkers in UC.

OBJECTIVE: Serologic tests are commonly used for screening Helicobacter pylori infection because they not only provide quick results but also are inexpensive. A new latex agglutination serum antibody assay (LZ test) has been developed and it is expected to be as effective as conventional assays. This study aimed to calculate a reliable cutoff value for the LZ test and to estimate the sensitivity and specificity of the cutoff value in screening adolescents for H. pylori infection in Japan.
METHODS: We screened junior high school students in Akita Prefecture, Japan, for H. pylori infection. We used the data of 213 such students who underwent H. pylori stool antigen (HpSA) tests in 2016. The students who had positive results with HpSA tests were diagnosed with H. pylori infection. Of the 213 students, 209 underwent the LZ test.
RESULTS: The prevalence rate of H. pylori infection was 3.8% (8/209). The area under the curve for the LZ test was 0.88. The cutoff value of the LZ test was determined to be 3.1 U/mL. At this value, the sensitivity and specificity were 87.5 and 91.5%, respectively.
CONCLUSIONS: The accuracy of the LZ test in adolescents was well balanced for sensitivity and specificity as well as for tolerable results.

OBJECTIVE: For analysis of blood concentrations of everolimus, many hospital laboratories use either latex agglutination turbidimetric immunoassay (LTIA) or electrochemiluminescence immunoassay (ECLIA). However, no studies have compared both immunoassay methods under the same conditions. Accordingly, in this study, we compared everolimus blood concentrations obtained by LTIA and ECLIA in renal transplant patients.
METHODS: Blood samples (n = 230) from 60 renal transplant patients (19 female and 41 male) were evaluated using both immunoassays. Subsequently, we switched the assay for detection of everolimus blood concentrations from LTIA to ECLIA as a clinical application. Three quality control (QC) samples for LTIA were analysed using ECLIA, and 3 QC samples for ECLIA were analysed using LTIA.
RESULTS: The Deming regression of ECLIA versus LTIA generated the following parameters: slope, 1.0067 and intercept, 1.7489 ng/mL, in the analysis of 230 samples. Bland-Altman analysis showed an average positive bias of 1.73 ng/mL between ECLIA and LTIA. When the clinical apparatus was switched from LTIA to ECLIA, the average everolimus blood concentration assayed by LTIA before switching was 3.57 ng/mL, whereas that by ECLIA after switching in the same patients taking the same daily dose (mean: 1.43 mg/day) was 5.85 ng/mL. The QCs assayed using LTIA were lower by an average of 67.3% (range: 55.8%-79.5%) for ECLIA, and in the same 230 samples from patients, the everolimus blood concentrations assayed by LTIA were lower by an average of 67.4% (range: 37.1%-114.5%) of ECLIA.
CONCLUSIONS: Analysis of everolimus concentrations by immunoassays with high precision and accuracy is required to ensure long-term survival of transplant recipients. Although the concentrations of QCs and calibrators of everolimus in LTIA were previously corrected to 70% concentration because of cross-reactivity with everolimus metabolites, these adjustments may need to be reviewed.