The Diagnostic Dilemma of Traumatic Lumbar Puncture: Current Standing of Cerebrospinal Fluid Leukocyte Corrections and Our Experience With Cerebrospinal Fluid Biomarkers

Meta-analysis of Cerebrospinal Fluid Cell Count and Biochemistry to Diagnose Meningitis in Infants Aged < 90 Days

OBJECTIVE

 Cerebrospinal fluid (CSF) white blood cell (WBC) count, protein, and glucose (cytochemistry) are performed to aid in the diagnosis of meningitis in young infants. However, studies have reported varying diagnostic accuracies. We assessed the diagnostic accuracy of CSF cytochemistry in infants below 90 days and determined the certainty of evidence.

STUDY DESIGN

 We searched PubMed, Embase, Cochrane Library, Ovid, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Scopus databases in August 2021. We included studies that evaluated the diagnostic accuracy of CSF cytochemistry compared with CSF culture, Gram stain, or polymerase chain reaction in neonates and young infants <90 days with suspected meningitis. We pooled data using the hierarchical summary receiver operator characteristic (ROC) model.

RESULTS

 Of the 10,720 unique records, 16 studies were eligible for meta-analysis, with a cumulative sample size of 31,695 (15 studies) for WBC, 12,936 (11 studies) for protein, and 1,120 (4 studies) for glucose. The median (Q1, Q3) specificities of WBC, protein, and glucose were 87 (82, 91), 89 (81, 94), and 91% (76, 99), respectively. The pooled sensitivities (95% confidence interval [CI]) at median specificity of WBC count, protein, and glucose were 90 (88, 92), 92 (89, 94), and 71% (54, 85), respectively. The area (95% CI) under ROC curves were 0.89 (0.87, 0.90), 0.87 (0.85, 0.88), and 0.81 (0.74, 0.88) for WBC, protein, and glucose, respectively. There was an unclear/high risk of bias and applicability concern in most studies. Overall certainty of the evidence was moderate. A bivariate model-based analysis to estimate the diagnostic accuracy at specific thresholds could not be conducted due to a paucity of data.

CONCLUSION

 CSF WBC and protein have good diagnostic accuracy for the diagnosis of meningitis in infants below 90 days of age. CSF glucose has good specificity but poor sensitivity. However, we could not identify enough studies to define an optimal threshold for the positivity of these tests.

KEY POINTS

· Median specificity of CSF leucocyte count, protein and glucose are similar in young infants.. · At median specificity, CSF leukocyte count and protein are more sensitive than glucose.. · Owing to inadequate data, bivariate modelling to suggest optimal diagnostic thresholds is not possible..

Diagnostic Accuracy of Procalcitonin in Bacterial Infections of the CNS: An Updated Systematic Review, Meta-Analysis, and Meta-Regression

OBJECTIVES

To evaluate diagnostic accuracy of serum and cerebrospinal fluid (CSF) procalcitonin for diagnosing CNS bacterial infections.

DATA SOURCES

We searched MEDLINE, Cochrane Central Register of Controlled Trials, and International Web of Science databases from January 1, 2016, to September 30, 2022.

STUDY SELECTION

Randomized controlled trials and observational studies, either prospective or retrospective, focusing on procalcitonin as a biomarker for CNS infections.

DATA EXTRACTION

We screened and extracted studies independently and in duplicate. We assessed risk of bias using the revised Quality Assessment for Studies of Diagnostic Accuracy tool. Data for diagnostic sensitivity and specificity were pooled using the bivariate or hierarchical model, as appropriate.

DATA SYNTHESIS

Of 5,347 citations identified, 23 studies were included. Overall, CSF procalcitonin showed slightly higher pooled sensitivity, specificity, and positive likelihood ratio compared with serum procalcitonin. In adults, pooled sensitivity of CSF procalcitonin was 0.89 (95% CI, 0.71-0.96), specificity 0.81 (95% CI, 0.66-0.91); pooled sensitivity of serum procalcitonin was 0.82 (95% CI, 0.58-0.94), specificity 0.77 (95% CI, 0.60-0.89). In children, pooled sensitivity of CSF procalcitonin was 0.96 (95% CI, 0.88-0.99), specificity 0.91 (95% CI, 0.72-0.97); pooled sensitivity of serum procalcitonin was 0.90 (95% CI, 0.75-0.97), specificity 0.83 (95% CI, 0.67-0.92). In post-neurosurgical patients, pooled sensitivity of CSF procalcitonin was 0.82 (95% CI, 0.53-0.95), specificity 0.81 (95% CI, 0.63-0.91); pooled sensitivity of serum procalcitonin was 0.65 (95% CI, 0.33-0.88), specificity 0.61 (95% CI, 0.41-0.78). Logistic regression revealed between-study heterogeneity higher for serum than CSF procalcitonin. For the latter, threshold variability was found as source of heterogeneity.

CONCLUSIONS

In children and critical post-neurosurgical patients, CSF procalcitonin gains superior sensitivity and specificity compared with serum procalcitonin. Overall, CSF procalcitonin appears to have a higher pooled positive likelihood ratio compared with serum procalcitonin.

Rapid and Efficient Computation of Cell Paths During Ultrasonic Focusing

This biophysical analysis explores the first-principles physics of movement of white blood cell sized particles, suspended in an aqueous fluid and experiencing progressive or standing waves of acoustic pressure. In many current applications the cells are gradually nudged or herded toward the nodes of the standing wave, providing a degree of acoustic focusing and concentration of the cells in layers perpendicular to the direction of sound propagation. Here the underlying biomechanics of this phenomenon are analyzed specifically for the viscous regime of water and for small diameter microscopic spheroids such as living cells. The resulting mathematical model leads to a single algebraic expression for the creep or drift velocity as a function of sound frequency, amplitude, wavelength, fluid viscosity, boundary dimensions, and boundary reflectivity. This expression can be integrated numerically by a simple and fast computer algorithm to demonstrate net movement of particles as a function of time, providing a guide to optimization in a variety of emerging applications of ultrasonic cell focusing.

Interpretation of white blood cell counts in the cerebrospinal fluid of neonates with traumatic lumbar puncture: a retrospective cohort study

BACKGROUND

Difficulty in interpreting white blood cell (WBC) counts in cerebrospinal fluid (CSF) complicates the diagnosis of neonatal meningitis in traumatic lumbar punctures (LP). The aim of our study was to determine the correction factor for WBC counts in traumatic LP that offers the greatest diagnostic efficacy in meningitis.

METHODS

We conducted a retrospective observational study of LP in neonates between January 2014 and December 2020. Traumatic LP was defined as a red blood cell (RBC) count ≥ 1,000 cells/mm³ CSF and pleocytosis as WBCs ≥ 20 cells/mm³ CSF. The CSF RBC:WBC ratio was analyzed by linear regression to determine a new correction factor. Cell count adjustments were also studied using the 500:1, the 1,000:1 ratio method, and the peripheral blood RBC:WBC ratio, using ROC curves and studies of accuracy (sensitivity and specificity).

RESULTS

Overall, 41.0% of the 1,053 LPs included in the study were traumatic. The best results for effective WBC correction were the method based on the peripheral blood ratio (sensitivity = 1.0 and specificity = 0.9 for bacterial meningitis and sensitivity = 0.8 and specificity = 0.9 for viral meningitis) and the 400:1 ratio (sensitivity = 1.0 and specificity = 0.8 for bacterial meningitis and sensitivity = 0.8 and specificity = 0.8 for viral meningitis) obtained from linear regression (95% CI 381.7-427.4; R2 = 0.7).

CONCLUSION

Both the peripheral blood correction and the 400:1 correction reduce the number of neonates classified with pleocytosis who were not eventually diagnosed with meningitis. Both methods might be a useful tool to clarify the neonatal meningitis diagnosis, offering neonatologists the possibility to assess the WBC count in traumatic LP.