Invisible hemolysis in serum samples interferes in NSE measurement

Managing hemolysis in serum neuron-specific enolase measurements - an automated algorithm for routine practice

Neuron-specific enolase (NSE) derived from neurons and peripheral neuroendocrine cells is a biomarker for neuroendocrine tumors and for prognostication in comatose cardiac arrest survivors. However, as platelets and erythrocytes contain NSE, hemolysis causes falsely elevated NSE. We used native serum and hemolysate derived from the same patients to make serial dilutions, and subsequently measured NSE (mNSE) and hemolytic index (HI) in each dilution. An algorithm suitable for the laboratory information system was developed based on the mNSE, HI and the estimated gradient of hemolytic interference from 30 patients. We estimated the associated uncertainty of the corrected NSE (cNSE) results based on the observed range of the gradient and derived an equation for cNSE for samples with limited hemolysis (i.e. 5 < HI ≤ 30): cNSE = mNSE - HI × (0.34 ± 0.23) µg/L. By semi-quantitatively grading the contribution from limited hemolysis, a texted result noting the hemolysis-associated degree of uncertainty can accompany the cNSE result. The major challenge of hemolysis when using serum NSE as a biomarker can be managed using an automated algorithm for correction of NSE results based on degree of hemolysis. However, laboratorians and clinicians should be aware of the limitations associated with in vivo hemolysis.

Neuron-specific enolase levels immediately following cardiovascular surgery is modulated by hemolysis due to cardiopulmonary bypass, making it unsuitable as a brain damage biomarker

Neuron-specific enolase (NSE) is one of the biomarkers used as an indicator of brain disorder, but since it is also found in blood cell components, there is a concern that a spurious increase in NSE may occur after cardiovascular surgery, where cardiopulmonary bypass (CPB) causes hemolysis. In the present study, we investigated the relationship between the degree of hemolysis and NSE after cardiovascular surgery and the usefulness of immediate postoperative NSE values in the diagnosis of brain disorder. A retrospective study of 198 patients who underwent surgery with CPB in the period from May 2019 to May 2021 was conducted. Postoperative NSE levels and Free hemoglobin (F-Hb) levels were compared in both groups. In addition, to verify the relationship between hemolysis and NSE, we examined the correlation between F-Hb levels and NSE levels. We also examined whether different surgical procedures could produce an association between hemolysis and NSE. Among 198 patients, 20 had postoperative stroke (Group S) and 178 had no postoperative stroke (Group U). There was no significant difference in postoperative NSE levels and F-Hb levels between Group S and Group U (p = 0.264, p = 0.064 respectively). F-Hb and NSE were weakly correlated (r = 0.29. p < 0.01). In conclusion, NSE level immediately after cardiac surgery with CPB is modified by hemolysis rather than brain injury, therefore it would be unreliable as a biomarker of brain disorder.

The use of neurone specific enolase to prognosticate neurological recovery and long term neurological outcomes in OOHCA patients

Introduction

Hypoxic-ischaemic brain injury (HIBI), is a common sequalae following out-of-hospital cardiac arrest (OOHCA), it is reported as the cause of death in 68% of patients who survive to ICU admission, while other patients can be left with permanent neurological disability. Prediction of neurological outcome follows a multimodal approach, including use of the biomarker, neurone specific enolase (NSE). There is however no definitive cut-off value for poor neurological outcome, and little research has analysed NSE and long-term outcomes in survivors. We investigated an NSE threshold for poor short-term neurological outcome and the relationship between NSE and poor neurological outcome in survivors.

Methods

A retrospective study was conducted of all adult OOHCA patients admitted to the Royal County Sussex Hospital ICU between April 2017 and November 2018. NSE levels, Targeted Temperature Management (TTM), cross-sectional imaging, mortality and GCS on ICU discharge were recorded. Assessment of neurological function after a median of 19 months (range 14-32 months) post ICU discharge was undertaken following ICU discharge and related to NSE.

Results

NSE levels were measured in 59 patients; of these 36 (61%) had a poor neurological outcome due to hypoxic ischaemic brain injury. Youden's index and ROC analysis established an NSE cut-off value of 64.5 μg/L, with AUC of 0.901, sensitivity of 77.8% and specificity of 100%. Follow-up of 26 survivors after 19 months did not show a significant relationship between NSE after OOHCA and long-term neurological outcome.

Conclusion

Our results show that NSE >64.5 µg/L has a poor short-term neurological outcome with 100% specificity. Whilst limited by a low sample size, NSE in survivors showed no relationship with neurological outcome post OOHCA in the long term.

Confounders for prognostic accuracy of neuron-specific enolase after cardiac arrest: A retrospective cohort study

AIM

To evaluate neuron-specific enolase (NSE) thresholds for prediction of neurological outcome after cardiac arrest and to analyze the influence of hemolysis and confounders.

METHODS

Retrospective analysis from a cardiac arrest registry. Determination of NSE serum concentration and hemolysis-index (h-index) 48-96 hours after cardiac arrest. Evaluation of neurological outcome using the Cerebral Performance Category score (CPC) at hospital discharge. Separate analyses considering CPC 1-3 and CPC 1-2 as good neurological outcome. Analysis of specificity and sensitivity for poor and good neurological outcome prediction with and without exclusion of hemolytic samples (h-index larger than 50).

RESULTS

Among 356 survivors three days after cardiac arrest, hemolysis was detected in 28 samples (7.9%). At a threshold of 60 µg/L, NSE predicted poor neurological outcome (CPC 4-5) in all samples with a specificity of 92% (86-95%) and sensitivity of 73% (66-79%). In non-hemolytic samples, specificity was 94% (89-97%) and sensitivity 70% (62-76%). At a threshold of 100 µg/L, specificity was 98% (95-100%, all samples) and 99% (95-100%, non-hemolytic samples), and sensitivity 58% (51-65%) and 55% (47-63%), respectively. Possible confounders for elevated NSE in patients with good neurological outcome were ECMO, malignancies, blood transfusions and acute brain diseases. Nine patients with NSE below 17 µg/L had CPC 5, all had plausible death causes other than hypoxic-ischemic encephalopathy.

CONCLUSIONS

NSE concentrations higher than 100 µg/L predicted poor neurological outcome with high specificity. An NSE less than 17 µg/L indicated absence of severe hypoxic-ischemic encephalopathy. Hemolysis and other confounders need to be considered.

INSTITUTIONAL PROTOCOL NUMBER

The local ethics committee (board name: Ethikkommission der Charité) approved this study by the number: EA2/066/23, approval date: 28th June 2023, study title "'ROSC' - Resuscitation Outcome Study."

Post-mortem detection of neuronal and astroglial biochemical markers in serum and urine for diagnostics of traumatic brain injury

Currently available epidemiological data shows that traumatic brain injury (TBI) represents one of the leading causes of death that is associated with medico-legal practice, including forensic autopsy, criminological investigation, and neuropathological examination. Attention focused on TBI research is needed to advance its diagnostics in ante- and post-mortem cases with regard to identification and validation of novel biomarkers. Recently, several markers of neuronal, astroglial, and axonal injury have been explored in various biofluids to assess the clinical origin, progression, severity, and prognosis of TBI. Despite clinical usefulness, understanding their diagnostic accuracy could also potentially help translate them either into forensic or medico-legal practice, or both. The aim of this study was to evaluate post-mortem pro-BDNF, NSE, UCHL1, GFAP, S100B, SPTAN1, NFL, MAPT, and MBP levels in serum and urine in TBI cases. The study was performed using cases (n = 40) of fatal head injury and control cases (n = 20) of sudden death. Serum and urine were collected within ∼ 24 h after death and compared using ELISA test. In our study, we observed the elevated concentration levels of GFAP and MAPT in both serum and urine, elevated concentration levels of S100B and SPTAN1 in serum, and decreased concentration levels of pro-BDNF in serum compared to the control group. The obtained results anticipate the possible implementation of performed assays as an interesting tool for forensic and medico-legal investigations regarding TBI diagnosis where the head injury was not supposed to be the direct cause of death.

Predicting poor neurological outcomes following out-of-hospital cardiac arrest using neuron-specific enolase and neurofilament light chain in patients with and without haemolysis

Aims

Hypoxic-ischaemic brain injury following out-of-hospital cardiac arrest (OHCA) is a common complication and a major cause of death. Neuron-specific enolase (NSE) and neurofilament light chain (NfL) are released after brain injury and elevated concentrations of both are associated with poor neurological outcome. We explored the influence of haemolysis on the prognostic performance of NSE and NfL.

Methods and results

The study is based on post hoc analyses of a randomized, single-centre, double-blinded, controlled trial (IMICA), where comatose OHCA patients of presumed cardiac cause were included. Free-haemoglobin was measured at admission to quantify haemolysis. NSE and NfL were measured after 48 h to estimate the extent of brain injury. Montreal Cognitive Assessment score (MoCA) was assessed to evaluate neurocognitive impairments. Seventy-three patients were included and divided into two groups by the median free-haemoglobin at admission. No group differences in mortality or poor neurological outcome were observed. The high-admission free-haemoglobin group had a significantly higher concentration of NSE compared to the low-admission free-haemoglobin group (27.4 µmol/L vs. 19.6 µmol/L, P = 0.03), but no differences in NfL. The performance of NSE and NfL in predicting poor neurological outcome were high for both, but NfL was numerically higher [area under the ROC (AUROC) 0.90 vs. 0.96, P = 0.09]. Furthermore, NfL, but not NSE, was inversely correlated with MoCA score, R2 = 0.21, P = 0.006.

Conclusion

High free-haemoglobin at admission was associated with higher NSE concentration after 48 h, but, the performance of NSE and NfL in predicting poor neurological outcome among OHCA patients were good regardless of early haemolysis. Only elevated NfL concentrations were associated with cognitive impairments.

Guidelines for Neuroprognostication in Comatose Adult Survivors of Cardiac Arrest

BACKGROUND

Among cardiac arrest survivors, about half remain comatose 72 h following return of spontaneous circulation (ROSC). Prognostication of poor neurological outcome in this population may result in withdrawal of life-sustaining therapy and death. The objective of this article is to provide recommendations on the reliability of select clinical predictors that serve as the basis of neuroprognostication and provide guidance to clinicians counseling surrogates of comatose cardiac arrest survivors.

METHODS

A narrative systematic review was completed using Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. Candidate predictors, which included clinical variables and prediction models, were selected based on clinical relevance and the presence of an appropriate body of evidence. The Population, Intervention, Comparator, Outcome, Timing, Setting (PICOTS) question was framed as follows: "When counseling surrogates of comatose adult survivors of cardiac arrest, should [predictor, with time of assessment if appropriate] be considered a reliable predictor of poor functional outcome assessed at 3 months or later?" Additional full-text screening criteria were used to exclude small and lower-quality studies. Following construction of the evidence profile and summary of findings, recommendations were based on four GRADE criteria: quality of evidence, balance of desirable and undesirable consequences, values and preferences, and resource use. In addition, good practice recommendations addressed essential principles of neuroprognostication that could not be framed in PICOTS format.

RESULTS

Eleven candidate clinical variables and three prediction models were selected based on clinical relevance and the presence of an appropriate body of literature. A total of 72 articles met our eligibility criteria to guide recommendations. Good practice recommendations include waiting 72 h following ROSC/rewarming prior to neuroprognostication, avoiding sedation or other confounders, the use of multimodal assessment, and an extended period of observation for awakening in patients with an indeterminate prognosis, if consistent with goals of care. The bilateral absence of pupillary light response > 72 h from ROSC and the bilateral absence of N20 response on somatosensory evoked potential testing were identified as reliable predictors. Computed tomography or magnetic resonance imaging of the brain > 48 h from ROSC and electroencephalography > 72 h from ROSC were identified as moderately reliable predictors.

CONCLUSIONS

These guidelines provide recommendations on the reliability of predictors of poor outcome in the context of counseling surrogates of comatose survivors of cardiac arrest and suggest broad principles of neuroprognostication. Few predictors were considered reliable or moderately reliable based on the available body of evidence.

Effects of centrifugation prior to pneumatic tube system transport on routine biochemical and immunological tests of susceptibility to hemolysis

BACKGROUND

Pneumatic tube system (PTS) may be associated with preanalytical hemolysis. The objective of this study was to evaluate the effects of PTS on biochemical and immunological tests susceptible to hemolysis and try to find ways to reduce the result bias caused by PTS.

METHODS

Laboratory parameters were compared between PTS without centrifuging group, PTS after centrifuging group, PTS with serum group, and hand-delivered (HD) group. Studies were performed to access the influence of different PTS transport frequencies on laboratory assays.

RESULTS

PTS transportation resulted in obviously increase in LDH (lactate dehydrogenase) and NSE (neuron-specific enolase) results (LDH: Bias = 17.95%, 95% confidence interval (CI) = -3.13-39.02; p < 0.001; NSE: Bias = 64.26%, 95% CI = -21.29-149.82; p < 0.001; respectively). After pre-centrifugation, no statistical difference was observed in LDH results (Bias = 2.83%, 95% CI = -13.00-18.65; p = 0.737). However, the bias of NSE still reach 19.16% (95% CI = -41.78-80.11), which exceeded the clinical acceptable range (p = 0.017). Both LDH(p = 0.931) and NSE(p > 0.999) show no statistical difference between PTS with serum group and HD group (LDH: Bias = -1.60%, 95% CI = -6.00-2.81; NSE: Bias = -3.68%, 95% CI = -11.35-3.99).

CONCLUSION

PTS can lead to falsely increased LDH and NSE test results. Only loading the centrifuged upper serum in new tubes during PTS transport can eliminate the results bias of NSE.

MicroRNA-9-3p: a novel predictor of neurological outcome after cardiac arrest

AIMS

Resuscitated out-of-hospital cardiac arrest (OHCA) patients who remain comatose after hospital arrival are at high risk of mortality due to anoxic brain injury. MicroRNA are small-non-coding RNA molecules ultimately involved in gene-silencing. They show promise as biomarkers, as they are stable in body fluids. The microRNA 9-3p (miR-9-3p) is associated with neurological injury in trauma and subarachnoid haemorrhage.

METHODS AND RESULTS

This post hoc analysis considered all 171 comatose OHCA patients from a single centre in the target temperature management (TTM) trial. Patients were randomized to TTM at either 33°C or 36°C for 24 h. MicroRNA-9-3p (miR-9-3p) was measured in plasma sampled at admission and at 28, 48, and 72 h. There were no significant differences in age, gender, and pre-hospital data, including lactate level at admission, between miR-9-3p level quartiles. miR-9-3p levels changed markedly following OHCA with a peak at 48 h. Median miR-9-3p levels between TTM 33°C vs. 36°C were not different at any of the four time points. Elevated miR-9-3p levels at 48 h were strongly associated with an unfavourable neurological outcome [OR: 2.21, 95% confidence interval (CI): 1.64-3.15, P < 0.0001). MiR-9-3p was inferior to neuron-specific enolase in predicting functional neurological outcome [area under the curve: 0.79 (95% CI: 0.71-0.87) vs. 0.91 (95% CI: 0.85-0.97)].

CONCLUSION

MiR-9-3p is strongly associated with neurological outcome following OHCA, and the levels of miR-9-3p are peaking 48 hours following cardiac arrest.

Plasma Neuron-Specific Enolase is not a reliable biomarker for staging Trypanosoma brucei rhodesiense sleeping sickness patients

Objective

Currently, the only available staging criterion for T. b. rhodesiense requires a lumber puncture to collect and later examine cerebrospinal fluid (CSF). This study examined the potential of plasma Neuron-Specific Enolase (NSE) in discriminating between early and late-stage patients.

Results

When median NSE levels were compared between early and late-stage patients, results showed a significant (P < 0.02) upregulation among late-stage patients (599.8 ng/mL). No significant differences (P > 0.9) in NSE levels were observed between early-stage patients (300 ng/mL) and controls (454 ng/mL). We used Receiver Operator Characteristic (ROC) curves to explore the likelihood of using plasma NSE as a potential stage biomarker in discriminating between early and late-stage HAT patients. Our results showed that NSE demonstrated an area under the curve (AUC) of 0.702 (95% CI 0.583–0.830). A high staging accuracy for NSE was obtained by using a cutoff of > 346.5 ng/mL with a sensitivity of 68.6% (95% CI 55–79.7%) and a specificity of 93.3% (95% CI 70.2–99.7%). Although our results demonstrate that plasma NSE is upregulated in T. b. rhodesiense sleeping sickness patients, its value in discriminating between late and early-stage patients is limited. However, future studies could consider improving its specificity by combining it with other identified plasma biomarkers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-05981-w.

Development and validation of a simple correction method for the measurement of neuron-specific enolase in hemolyzed serum samples

The Neuron-specific enolase (NSE), a biomarker of neuroendocrine tumors or ischemic brain damage, has limited clinical applicability since its measurement is overestimated by hemolysis. In this study, an NSE correction method was developed for hemolyzed samples. The NSE concentration and the hemolysis index (HI) of serum were measured before and after spiking a hemolysate prepared with red blood cells from the serum-separating tube and extrapolating the NSE value corresponding to a HI of zero. To validate the approach (n = 46), NSE concentrations and HI were measured before (NSE0 and HI0) and after spiking the samples with 50 µL (HIA, NSEA) and 100 µL (HIB, NSEB) of hemolysate. A linear regression analysis was performed between (HIA, NSEA) and (HIB, NSEB). The y-intercept was taken as the corrected NSE concentration (NSEintercept) and compared with NSE0. On the same samples, the equation of Tolan et al. was applied and the corrected values of NSE (NSEcorr) were compared to NSE0. The average bias (±SD) between the NSE0 and the NSEintercept was equal to -3.2% (± 14.3) versus 34.6% (± 19.8) against the NSEcorr. Applying the allowable total error proposed by the European Federation of Laboratory Medicine, 72% of the NSE results were adequately corrected while the reference method corrected only 8.7% of the results. The individualized hemolysis correction method developed is simple, fast, requires one serum-separating tube, provides increased accuracy compared to the method described by Tolan et al. and should improve the quality of patient care.

A Simple and Cost-Effective Method for Measuring Hemolysis in Biobank Serum Specimens

Background: During sampling and processing, blood samples can be affected by hemolysis. Information is lacking regarding hemolysis for biobank samples. There is a need for a method that can easily measure hemoglobin as an indicator of hemolysis in stored samples before they are included in research projects. In this study we present a simple method for estimating hemolysis and investigate the effect of centrifugation speeds and temperatures on sample turbidity that commonly interferes with measurements. Methods: Using a variation of the Beer-Lambert law, we quantified the hemoglobin concentration in 75 long-term stored samples at a wavelength of 414 nm with a NanoDrop™ 8000 spectrophotometer. Owing to interference from turbidity, the samples underwent different treatments post-thawing: centrifugation at 10,000 and 20,000 g at two different temperatures (4°C and 19°C) for 15 minutes. In addition, freshly collected serum samples (n = 20) underwent a single freeze-thaw cycle, with hemoglobin measured prefreeze, post-thaw, and postcentrifugation. Kruskal-Wallis rank sum test groups and pairwise Wilcoxon rank test were used for statistical analysis. Results: A strong effect of centrifugation on the turbidity was shown for the long-term stored samples, however, this effect was independent of the temperature or centrifugation speeds. Centrifugation at 20,000 g for 15 minutes at 19°C reduced the turbidity up to 50%. A single freeze-thaw cycle in the fresh samples increased the optical density at 414 nm slightly, indicating a false increase of hemoglobin concentration. The following centrifugation reduced the concentration to less than the initial sample measurements, suggesting the presence of interference immediately after sampling. Conclusion: We describe here a simple and cost-effective NanoDrop-based method for measuring hemolysis levels intended for use in biobank facilities. We found that centrifugation, but not temperature, is a crucial step to reduce interference from turbidity.