Flow cytometry for the microscopy of body fluids in patients with suspected infection

Convergence of flow cytometry and bacteriology. Current and future applications: a focus on food and clinical microbiology

Since its development in the 1960s, flow cytometry (FCM) was quickly revealed a powerful tool to analyse cell populations in medical studies, yet, for many years, was almost exclusively used to analyse eukaryotic cells. Instrument and methodological limitations to distinguish genuine bacterial signals from the background, among other limitations, have hampered FCM applications in bacteriology. In recent years, thanks to the continuous development of FCM instruments and methods with a higher discriminatory capacity to detect low-size particles, FCM has emerged as an appealing technique to advance the study of microbes, with important applications in research, clinical and industrial settings. The capacity to rapidly enumerate and classify individual bacterial cells based on viability facilitates the monitoring of bacterial presence in foodstuffs or clinical samples, reducing the time needed to detect contamination or infectious processes. Besides, FCM has stood out as a valuable tool to advance the study of complex microbial communities, or microbiomes, that are very relevant in the context of human health, as well as to understand the interaction of bacterial and host cells. This review highlights current developments in, and future applications of, FCM in bacteriology, with a focus on those related to food and clinical microbiology.

Serous body fluid evaluation using the new automated haematology analyser Mindray BC-6800Plus

OBJECTIVES

Cellular analysis of body fluids (BF) has clinical relevance in several medical conditions. The objective of this study is twofold: (1) evaluate the analytical performance of the BF mode of Mindray BC-6800 Plus compared to manual counts under microscopy and (2) analyse if the high-fluorescent cell counts provided by the analyser (HF-BF) are useful to detect malignancy.

METHODS

A total of 285 BF was analysed: 250 corresponding to patients without neoplasia and 35 to patients with malignant diseases. Manual differential counts were performed in BF with ≥250 cells/μL. Percentages and absolute counts were obtained on the BC-6800Plus for total nucleated cells (TC-BF), mononuclear, polymorphonuclear and HF-BF. Statistical analysis was performed using Mann-Whitney U-test, Spearman's correlation, Passing-Bablok regression, Bland-Altman graph and ROC curve.

RESULTS

To compare manual and automatic total cell counts, samples were divided in three groups: <250, 250-1,000 and >1,000 cells/μL. Correlation was good in all cases (r=0.72, 0.73 and 0.92, respectively) without significant differences between both methods (p=0.65, 0.39 and 0.30, respectively). The concordance between methods showed values of 90%. Considering malignant samples, median HF-BF values showed significant higher values (102 cells/μL) with respect to non-malignant (4 cells/μL) (p<0.001). The cut-off value of 8.5 HF-BF/μL was able to discriminate samples containing malignant cells showing sensitivity and specificity values of 89 and 71%, respectively. Considering both, HF-BF and TC-BF values, sensitivity and specificity values were 100 and 53%, respectively.

CONCLUSIONS

This study reveals that the Mindray BC-6800Plus offers an accurate and acceptable performance, showing results consistent with the manual method. It is recommended to consider both HF-BF and TC-BF values for the screening of the microscopic evaluation to ensure the detection of all malignant samples.

Performance evaluation of automated cell counts compared with reference methods for body fluid analysis

OBJECTIVES

Cellular analysis of body fluids (BFs) can assist clinicians for the diagnosis of many medical conditions. The aim of this work is the evaluation of the analytical performance of the UF-5000 body fluid mode (UF-BF) analyzer compared to the gold standard method (optical microscopy, OM) and to XN-1000 (XN-BF), another analyzer produced by the same manufacturer (Sysmex) and with a similar technology for BF analysis.

METHODS

One hundred BF samples collected in K₃EDTA tubes were analyzed by UF-BF, XN-BF and OM. The agreement was evaluated using Passing and Bablok regression and Bland-Altman plot analysis. The receiver operating characteristic (ROC) curves were selected for evaluating the diagnostic agreement between OM classification and UF-BF parameters.

RESULTS

Comparison between UF-BF and OM, in all BF types, showed Passing and Bablok's slope comprised between 0.99 (polymorphonuclear cells count, PMN-BF) and 1.39 (mononuclear cells count, MN-BF), the intercepts ranged between 26.47 (PMN-BF parameter) and 226.80 (white blood cell count). Bland-Altman bias was comprised between 7.3% (total cell count, TC-BF) and 52.9% (MN-BF). Comparison between UF-BF and XN-BF in all BF showed slopes ranged between 1.07 (TC-BF and PMN-BF) and 1.16 (MN-BF), intercepts ranged between 8.30 (PMN) and 64.78 (WBC-BF). Bland-Altman bias ranged between 5.8 (TC-BF) and 21.1% (MN-BF). The ROC curve analysis showed an area under the curve ranged between 0.9664 and 1.000.

CONCLUSIONS

UF-BF shows very good performance for the differential counts of cells in ascitic, pleural and synovial fluids and therefore it is useful to screen and count cells in this type of BF.

Evaluation of automated synovial fluid total cell count and percent polymorphonuclear leukocytes on a Sysmex XN-1000 analyzer for identifying patients at risk of septic arthritis

BACKGROUND

Total cell counts (TC-BF) and percent polymorphonuclear cells (%PMN) of synovial fluid (SF) aspirates provide important cues for the timely diagnosis and management of septic arthritis. To facilitate faster turnaround time, we compared automated to manual TC-BF and differential counts in order to identify reporting cut-offs for automated TC-BF and %PMN that would allow release of automated results concordant with manual counts and differentials.

METHODS

Automated TC-BF and %PMN counts of a non-validated analyzer (Analyzer-B in STAT laboratory) were compared to a validated analyzer (Analyzer-A) and manual TC-BF counts and cytospin differentials. Concordance and %differences of Analyzer-B versus Analyzer-A and manual counts were assessed by linear regression analysis and Bland-Altman comparison.

RESULTS

Overall, automated and manual counts displayed good correlation. A majority of samples demonstrated unacceptable (>20%) differences between automated and manual counts at lower TC-BF (<10,000 cells/μl) and %PMN (<60%).

CONCLUSIONS

Based on good overall correlation and fewer samples with unacceptable (>20%) differences between automated and manual counts, we adopted TC-BF > 10,000 cells/μl and %PMN > 60% as cutoffs for reporting automated counts. These cutoffs minimize differences between automated and manual cell counts and differentials and would allow rapid automated reporting in the vast majority of septic arthritis cases.

Lack of harmonization in high fluorescent cell automated counts with body fluids mode in ascitic, pleural, synovial, and cerebrospinal fluids

INTRODUCTION

Cellular analysis in body fluids (BFs) provides important diagnostic information in various pathological settings. This study was hence aimed at comparing automated cell count obtained with Mindray BC-6800 (BC-BF) vs Sysmex XN-series (XN-BF) and evaluating other quantitative and qualitative information provided by these analyzers in ascitic (AF), pleural (PF), synovial (SF), and cerebrospinal (CSF) fluids.

METHODS

Three hundred and fifty-one samples (99 AFs, 45 PFs, 75 SFs, and 132 CSFs) were analyzed in parallel with BC-BF, XN-BF, and optical microscopy (OM). The study also included the assessment of diagnostic agreement among BC-BF, XN-BF, and OM.

RESULTS

The comparison of BC-BF vs XN-BF yielded slopes of Passing and Bablok regression always comprised between 0.9 and 1.0 except for EO-BF and HF-BF, whilst the intercepts ranged from -0.4 for MN-BF and 12.0 for PMN-BF. The bias was comprised between -103.3% and 67.1% for HF-BF and EO-BF, respectively. A significant bias was found for TC-BF, WBC-BF, HF-BF (negative bias) and for PMN-BF and EO-BF (positive bias). The agreement (Cohen's kappa) between XN-BF and BC-BF was always ≥0.7, ranging between 0.87 in CSFs and 0.94 in AFs, and that with OM was similar (ie, 0.85 and 0.96).

CONCLUSION

The cytometric analysis of BF samples using BC-BF and XN-BF is clinically favorable when appropriately combined with OM. Quantitative and qualitative parameters displayed optimal agreement, whilst instrument-specific cut-offs should be defined and implemented for HF-BF and EO-BF. Further efforts should be made for achieving better harmonization in cytometric analysis of BF samples.

Two-site evaluation of the diagnostic performance of the Sysmex XN Body Fluid (BF) module for cell count and differential in Cerebrospinal Fluid

INTRODUCTION

Cellular analysis in cerebrospinal fluid (CSF) provides important diagnostic information in many pathological settings. The aim of this two-site study was to evaluate the Sysmex XN Body Fluid mode (XN-BF) for cell analysis of CSF compared to light microscopy (LM).

METHODS

Two hundred and seven consecutive CSF samples were analyzed in parallel with XN-BF and LM. The study also included the estimation of the limit of blank (LoB), limit of detection (LoD), limit of quantitation (LoQ), carry-over and linearity of XN-BF module.

RESULTS

LoQ of white blood cells (WBC) was 3×10⁶  cells/L; linearity was good and carry-over negligible. XN-BF parameters were compared to LM for the following cell classes: total cells, WBC, polymorphonuclear (PMN), and mononuclear (MN) cells. The bias ranged from 1.3 to 15.2×10⁶  cells/L. The receiver operating characteristics curve analysis for WBC showed an area under the curve of 0.98, and the global diagnostic agreement was 95% at a cutoff of 5×10⁶  cells/L.

CONCLUSIONS

XN-BF provides rapid and accurate counts in clinically relevant ranges of CSF values, thus providing a valuable alternative to conventional LM analysis. However, microscopic review remains advisable in samples with abnormal cell counts or high fluorescent (HF-BF) cell parameter exceeding 5×10⁶  cells/L.

Evaluation of biological fluid analysis using the sysmex XN automatic hematology analyzer

BACKGROUND

Hematological cytometers with a biological fluid module could potentially correct the limitations of the manual chamber method. This study evaluates the agreement between the manual technique and the Sysmex XN-1000 analyzer for white blood cell (WBC) and red blood cell (RBC) counts, as well as for leukocyte differentiation in different types of fluids. This study also evaluates the advantages of incorporating the technique in routine laboratory work.

METHODS

One hundred and three fluid samples examined were 45 ascite (AF), 21 synovial (SF), 33 pleural (PF), and 31 cerebrospinal (CSF) fluid samples. All cell counting was performed with a Sysmex XN-1000 and a Fuchs-Rosenthal counting chamber. May Gründwald-Giemsa stain was used for manual WBC differentiation. The manual analysis data were obtained in duplicate by the same two observers. Passing-Bablok regression and the Kappa index were used to evaluate the interchangeability and concordance.

RESULTS

Good agreement was observed for WBC differentiation in all fluids and for WBC counts in SF and PF. An optimal Kappa index was obtained, which indicated agreement and clinical significance for WBC and RBC counts in CSF and for RBC counts in PF. There was disagreement for WBC and RBC analysis in AF, with significantly higher results from the Sysmex XN-1000 than from the manual method. A reduction in laboratory response time was observed when using the automatic method.

CONCLUSIONS

Except for AF, the Sysmex XN-1000 results agree with those of the manual method, although to different degrees depending on the fluid type. © 2017 International Clinical Cytometry Society.

Clinical chorioamnionitis at term VII: the amniotic fluid cellular immune response

OBJECTIVES

1) To characterize the cellular composition of the amniotic fluid of patients diagnosed with clinical chorioamnionitis at term, as a function of the presence or absence of microorganisms determined by cultivation techniques, and 2) to characterize the cytokine production by white blood cells present in the amniotic fluid using flow cytometry-based techniques.

MATERIALS AND METHODS

Amniotic fluid samples from 20 women who had the diagnosis of clinical chorioamnionitis at term were analyzed using cultivation techniques (for aerobic and anaerobic bacteria as well as genital Mycoplasmas). Amniotic fluid IL-6 concentrations were determined by an enzyme-linked immunosorbent assay. Amniotic fluid leukocytes were visualized by using hematoxylin and eosin staining and immunofluorescence. Immunophenotyping of surface markers and cytokines was performed in amniotic fluid leukocytes using flow cytometry.

RESULTS

1) Neutrophils (CD45+CD15+ cells) were the most common leukocyte subset found in the amniotic fluid, followed by monocytes (CD45+CD14+ cells); other white blood cells (such as lymphocytes and natural killer cells) were scarce in the amniotic fluid; 2) the absolute counts of neutrophils and monocytes were significantly higher in patients with microorganisms found in the amniotic fluid than in those without detectable microorganisms, using cultivation techniques; 3) there was a significant correlation between the absolute counts of neutrophils and monocytes determined by flow cytometry (Spearman's correlation=0.97; P<0.001); 4) there was a significant correlation between the absolute white blood cell count determined with a hemocytometer chamber and by flow cytometric analysis (Spearman's correlation=0.88; P<0.001); and 5) the profile of cytokine expression differed between monocytes and neutrophils; while neutrophils predominantly produced TNF-α and MIP-1β, monocytes expressed higher levels of IL-1β and IL-1α.

CONCLUSION

Flow cytometry analysis of the amniotic fluid of patients with intra-amniotic infection and clinical chorioamnionitis at term demonstrated that neutrophils and monocytes are the most common cells participating in the inflammatory process. We have characterized, for the first time, the differential cytokine expression by these cells in this important complication of pregnancy.

Evaluation of Mindray BC-6800 body fluid mode for automated cerebrospinal fluid cell counting

Background:

Cellular analysis in cerebrospinal fluid (CSF) provides important diagnostic information in various medical conditions. The aim of this study was to evaluate the application of Mindray BC-6800 body fluid (BF) mode in cytometric analysis of CSF compared to light microscopy (LM).

Methods:

One hundred and twenty-nine consecutive CSF samples were analyzed by BC-6800-BF mode as well as by LM. The study also included limits of blank (LoB), limit of detection (LoD), limit of quantitation (LoQ), carryover and linearity.

Results

White blood cells LoQ was 4.0×10

Conclusions:

BC-6800-BF offers rapid and accurate counts in clinically relevant concentration ranges, replacing LM for most samples. However, in samples with abnormal cell counts or with abnormal white blood cell differential scattergrams the need to microscopic review for a correct clinical outcome remains.