Clinical performance evaluation of serum amyloid A module of Mindray BC-7500CS automated hematology analyzer

Abstract

Background: Laboratory detection of high values of serum amyloid A (SAA) is impaired by the hook effect. In response to this problem, Mindray has launched the new generation BC-7500CS automated hematology analyzer with an SAA autodilution (SAA-D) function. The present study aimed to verify the performance of the SAA module.

Methods: Venous whole-blood specimens anticoagulated with EDTA-K2 were randomly collected from outpatients and inpatient of the Children's Hospital of Nanjing Medical University (CH). Background, repeatability, precision, linear range, intermode comparison, and interference of the SAA module of the Mindray BC-7500CS were evaluated, and the performance of the SAA-D function was verified.

Results: The Mindray BC-7500CS showed an SAA background of 0.14 mg/L, well below that claimed by the manufacturer. Repeatability of SAA with standard deviation (SD) <0.6 mg/L and coefficient of variation (CV) <6%, the quality control (QC) precision was less than 8%. The measured value of the linear range was essentially consistent with the theoretical value, and the maximum measured values could reach 1932.38 mg/L. The deviation between whole-blood mode and micro-whole-blood mode was small (r=0.999), and the SAA module displayed high anti-interference ability. In addition, the measured results of specimens with high SAA concentration diluted by SAA-D were close to those after manual dilution (r=0.993).

Conclusions: The SAA module of the Mindray BC-7500CS had excellent performance, and the SAA-D function was highly accurate at measuring specimens with high SAA concentration, enabling reliable SAA detection in the laboratory and clinical practice.

Keywords: BC-7500CS; SAA autodilution (SAA-D); high SAA concentration; performance evaluation; serum amyloid A (SAA).

Figure 1

Basic performance. (A) Background of SAA for Mindray BC-7500CS auto hematology analyzer. (B) Repeatability of SAA for Mindray BC-7500CS auto hematology analyzer. The scatter plot with bars on the left side indicates the SD when SAA ≤10 mg/L and the right side indicates the CV when SAA ≥10.01 mg/L. (C) Linearity of SAA (horizontal axis: theoretical concentration; vertical axis: original concentration). (D) Reportable range verification (horizontal axis: theoretical concentration; vertical axis: original concentration). (E) Inter-mode comparison of SAA with mode (horizontal axis: whole-blood mode; vertical axis: micro whole-blood mode). SAA, serum amyloid A; SD, standard deviation; CV, coefficient variation; CDR, complete blood count (CBC) + differential counts (DIFF)+ reticulocyte count (RET); CRP, C-reactive protein.

Figure 2

Interference study. Quantitative assessment of the interference level of different interferents (BIL, TG, VitC, RF, HAMA, HGB) on SAA. SAA, serum amyloid A; BIL, bilirubin; TG, total cholesterol; VitC, vitamin C; RF, rheumatoid factor; HAMA, human anti-mouse antibody; HGB, hemoglobin.

Figure 3

Methodological comparison of SAA results. Passing-Bablok regression analysis of detection results of the Mindray BC-7500CS and the Upper Ottoman-1000 (horizontal axis: SAA detection results of the Upper Ottoman-1000; vertical axis: SAA detection results of the Mindray BC-7500CS). SAA, serum amyloid A; CI, confidence interval.

Figure 4

Clinical applicability assessment. (A) Clinical origins of specimens with SAA concentration >280 mg/L; (B,C) clinical applicability analysis of cardiovascular surgery ICU specimens (Passing-Bablok regression analysis).; (D,E) clinical applicability analysis of ICU specimens (Passing-Bablok regression analysis). ICU, intensive care unit; SAA, serum amyloid A; CI, confidence interval.

Figure 5

Comparability between SAA autodilution (SAA-D) module and manual dilution. (A) Passing-Bablok regression diagram of specimens with high SAA concentration detected with the Mindray BC-7500CS and the Upper Ottoman-1000 (horizontal axis: SAA measurement results of the Upper Ottoman-1000; vertical axis: SAA measurement results of the Mindray BC-7500CS). (B) Passing-Bablok regression analysis diagram of the Mindray BC-7500CS and original concentration after dilution (horizontal axis: measured results of original concentration; vertical axis: measured results of the SAA-D module of the Mindray BC-7500CS). (C) Bland-Altman plot of the Mindray BC-7500CS and original concentration after dilution. SAA, serum amyloid A; CI, confidence interval.