Stabilization media increases recovery in paucicellular cerebrospinal fluid specimens submitted for flow cytometry testing

ClearLLab 10C reagents panel can be applied to analyze paucicellular samples by flow cytometry

The FDA-approved ClearLLab 10C Reagents Panel (Beckman Coulter) simplified the diagnosis of leukemias and lymphomas by flow cytometry. However, the requirement of using 3 × 106 cells/mL cannot be met for paucicellular samples. Therefore, we tested whether this 10-color panel can be reliably employed to analyze specimens with low cell concentrations. Serial dilutions of 16 samples (5 normal, 11 abnormal), yielding concentrations ranging from 3.0 × 106 to 0.0469 × 106 cells/mL (64-fold difference), were stained using the B-cell and T-cell panels of the ClearLLab 10C system, and mean fluorescence intensity (MFI) was measured for each antibody. For each cell dilution, the deviation from the value obtained with the FDA-approved concentration of 3.0 × 106 cells/mL was calculated. The agreement between the highest and lowest cell concentration data was evaluated by the Bland and Altman method, Pearson's and Spearman's correlation analyses, and linear regression. In all patients, the antigen expression pattern was similar at all cell concentrations tested, and the mean deviation of the MFI from the value obtained using 3.0 × 106 cells/mL never exceeded 10% for any of the antibodies. The Bland-Altman method demonstrated the similarity between results obtained with the FDA-approved cell concentration and a 64-fold diluted cell suspension, and a high positive correlation was found between MFI acquired under these two conditions. The tests utilizing the lowest density of cells yielded the same patterns of antigen expression in all patients as those performed with the FDA-approved concentration, documenting a 100% concordance between these two protocols. The ClearLLab 10C panel can reliably determine the expression of markers of leukemias and lymphomas in paucicellular samples containing as little as 0.0469 × 106 cells/mL (64-fold lower than the FDA-approved concentration). This finding markedly expands the applicability of the ClearLLab 10C platform in a clinical setting.

A noble extended stochastic logistic model for cell proliferation with density-dependent parameters

Cell proliferation often experiences a density-dependent intrinsic proliferation rate (IPR) and negative feedback from growth-inhibiting molecules in culture media. The lack of flexible models with explanatory parameters fails to capture such a proliferation mechanism. We propose an extended logistic growth law with the density-dependent IPR and additional negative feedback. The extended parameters of the proposed model can be interpreted as density-dependent cell-cell cooperation and negative feedback on cell proliferation. Moreover, we incorporate further density regulation for flexibility in the model through environmental resistance on cells. The proposed growth law has similarities with the strong Allee model and harvesting phenomenon. We also develop the stochastic analog of the deterministic model by representing possible heterogeneity in growth-inhibiting molecules and environmental perturbation of the culture setup as correlated multiplicative and additive noises. The model provides a conditional maximum sustainable stable cell density (MSSCD) and a new fitness measure for proliferative cells. The proposed model shows superiority to the logistic law after fitting to real cell culture datasets. We illustrate both conditional MSSCD and the new cell fitness for a range of parameters. The cell density distributions reveal the chance of overproliferation, underproliferation, or decay for different parameter sets under the deterministic and stochastic setups.

The influence of fixation of biological samples on cell count and marker expression stability in flow cytometric analyses

The most common applications of flow cytometry (FC) include diagnostics of haemato-oncological disorders, based on analysis of bone marrow, peripheral blood (PB), or cerebrospinal fluid (CSF) samples. A proper diagnostic process requires standardisation in setting the optimal time frame between material collection and the assay. Unfortunately, this might be difficult to achieve in daily practice due to unintended shipment delays, which might compromise large-scale multicentre studies. Thus, material fixation should be considered as a solution. The most widely used fixative agents are: paraformaldehyde, TransFix^®, Cyto-Chex^®, and serum-containing media. In this review, we attempted to summarise the literature data on the influence of sample storage under different temperatures and times combined with different fixation conditions on the cell count and marker expression levels. Based on the findings of several extensive studies employing fixed PB samples, it can be concluded that the performance of particular fixative greatly depends on the analysed marker and specific PB cell population expressing a given antigen. Preservation of absolute cell count was usually better in Cyto-Chex^®-fixed PB samples, whereas TransFix^® tended to better stabilise marker expression levels. CSF-based studies reveal that both serum-containing media and TransFix^® can prevent cellular loss and enhance FC-based detection of leptomeningeal localisations of haematological malignancies, the latter being more available and having longer shelf-life. As both cell count and marker expression level are the main determinants of quality of biological samples dedicated to FC analyses, it remains to be addressed by the investigators which is the fixative of choice for their specific research aims.

Reliable cerebrospinal fluid cytology reporting over an extended period: Is it possible by adding formol saline and ethylenediaminetetraacetic acid as cell preservative?

BACKGROUND

Reporting cerebrospinal fluid (CSF) cytology within a narrow time frame is crucial as it is often indicated in critically ill patients and moreover, the cells in CSF are highly labile and tend to decline rapidly on standing. However, due to various logistic issues, delay in reporting is inevitable at times, especially if ancillary tools are required. In this study, we examine the effect of using formol saline and ethylenediaminetetraacetic acid (EDTA) as a preservative on the cellular composition of CSF at 18, 24, and 48 hours of preservation.

METHODS

Thirty CSF specimens were examined within 2 hours of collection and this reading was recorded as time zero reading. The CSF specimens were then divided in three tubes with: (a) preservative:CSF ratio of 1:1; (b) preservative:CSF ratio of 1:5; and (c) no preservative. Total and differential leucocyte counts and immunocytochemistry were performed on the three specimens at 18, 24, and 48 hours and were compared with the readings at 0 hour.

RESULTS

Preserved CSF (in the ratio of 1:5) showed no significant decrease in the number of cells at 18 hours (P = .4), 24 hours (P = .3), and 48 hours (P = .1). Cellularity decreased by 8.5%, 22%, and 40% at 18, 24, and 48 hours, respectively. Cell morphology and antigenicity were well preserved at all the three time intervals.

CONCLUSION

Formol saline and EDTA, when mixed with the CSF in the ratio of 1:5, can preserve significant cellularity for up to 24 hours.

Quality Control of Immunophenotyping

Applications of immunophenotyping using flow cytometry offer precise and accurate means for providing information used to both diagnose and monitor disease; they serve as a standard platform for many research endeavors that study discrete populations of biological entities. The proper use of this highly sophisticated technology requires daily and ongoing monitoring of both the instrument and the methodology. Best practices for this begin with quality control (QC) procedures designed to set up and monitor the instrument performance, the reagents, and the results to ensure that they are working properly both on the day of use and over time. If the results of those QC procedures are outside of acceptable then recording the corrective action taken must also be included in the quality control records. Quality assurance (QA) is a way to know that the three phases of testing, namely, preanalytic, analytic, and postanalytic procedures, are being followed. This chapter describes the procedures used to assess quality control as it pertains to flow cytometry and immunophenotyping in all three phases of testing.

Detection of central nervous system involvement in childhood acute lymphoblastic leukemia by cytomorphology and flow cytometry of the cerebrospinal fluid

BACKGROUND

Therapy directed at the central nervous system (CNS) is an essential part of the treatment for childhood acute lymphoblastic leukemia (ALL). The current evaluation of CNS involvement based on cytomorphological examination of the cerebrospinal fluid (CSF) alone is not as sensitive with low cell counts as flow cytometric immunophenotyping (FCI) of the CSF. However, the importance of low CSF blasts counts at diagnosis is uncertain. We sought to determine the significance of FCI in relation to conventional morphological examination.

PROCEDURE

We retrospectively compared FCI of the CSF with cytomorphology at diagnosis or relapse of childhood ALL. All patients were diagnosed 2000-2012 in Stockholm or Umeå, Sweden. Clinical data were collected from medical records and the Nordic leukemia registry. Treatment assignment was based on morphological examination only.

RESULTS

The cohort was comprised of 214 patients with ALL. CSF involvement was detected by both methods in 20 patients, in 17 by FCI alone, and in one patient by cytomorphology alone. The relapse rate was higher for patients with negative cytology but positive FCI compared to those without CNS involvement using both methods. The difference was especially marked in the current protocol. However, none of the patients with negative CSF cytology but positive FCI had a CNS relapse.

CONCLUSIONS

FCI of the CSF increased the detection rate of CNS involvement of ALL approximately two times compared to cytomorphology. Patients with low-level CNS involvement may benefit from additional intensified systemic or CNS-directed therapy, but larger studies are needed.

Diagnostic utility of cerebrospinal fluid flow cytometry in patients with and without prior hematologic malignancy

Flow cytometry (FCM) is an adjunct study to routine analysis of cerebrospinal fluid (CSF) to investigate for involvement by a hematologic malignancy. However, in our experience, FCM only infrequently detects abnormalities in CSF. To help optimize resources without forfeiting clinically important data, we sought to determine evidence-based indications and criteria for performing FCM on CSF. FCM results of 316 consecutive CSF specimens were retrospectively reviewed and correlated with clinical history, total nucleated cell (TNC) counts, and results of concurrent cytologic review. Of 255 samples adequate for analysis, 54% were from patients with a prior history of hematologic malignancy, of which 12% (17 cases) were abnormal by FCM. Corresponding TNC counts among samples with abnormal FCM ranged from 0-1050 cells/µL, and only 44% showed abnormal morphology on concurrent cytology. Of the remaining 46% of samples from patients with no known history of hematologic malignancy who had CSF sampling for neurological indications, only one (1%) was abnormal by FCM. This specimen had an elevated TNC count (39 cells/µL) but lacked clearly abnormal findings on concurrent cytology. These results support the use of CSF FCM only in patients with a history of hematologic malignancy or, in the absence of such a history, in samples showing pleocytosis. If these criteria were applied to the current cohort using a TNC count cut-off of >5 cells/µL, 23% of samples would have been deferred from testing, resulting in decreased cost, improved efficiency, and reduction in the need for unnecessary testing without a negative impact on clinical care.