Cerebrospinal fluid lactate level as a diagnostic biomarker for bacterial meningitis in children

Correlation between cerebrospinal fluid abnormalities before ventriculoperitoneal shunt and postoperative intracranial infection in adult patients with hydrocephalus: A clinical study

Objective

To identify the relationship between preoperative cerebrospinal fluid (CSF) leukocyte, chloride, glucose, aspartate aminotransferase, lactate dehydrogenase, adenosine deaminase, lactic acid and protein levels and ventriculoperitoneal shunt infection.

Methods

Records of 671 consecutive adult patients who underwent ventriculoperitoneal shunt surgery for the treatment of hydrocephalus at Zhujiang Hospital affiliated with Southern Medical University from January 2011 to March 2022 were reviewed. The patients were divided into infection and non-infection groups based on the presence of postoperative infection. For all patients, we analyzed age; sex; primary disease; preoperative CSF leukocyte, chloride, glucose, aspartate aminotransferase, lactate dehydrogenase, adenosine deaminase, lactic acid and protein levels; postoperative temperature; and postoperative infection.

Results

A total of 397 patients were included, 28 (7.05%) of whom had an infection within 6 months of the operation and the remaining had no infection. There was no significant difference in age, sex, primary disease, leukocyte, chloride ion, aspartate aminotransferase, lactate dehydrogenase, adenosine deaminase and protein levels in CSF between infection group and non-infection group (p > 0.05). The postoperative infection rate of patients with CSF glucose < 2.8 mmol/L (x ² = 11.650, p = 0.001) and CSF lactic acid >2.8 mmol/L (x ² = 12.455, p < 0.001) was higher than that of patients with CSF glucose level ≥2.8 mmol/L and CSF lactic acid level in the range of (1-2.8) mmol/L, respectively, with statistical difference. Compared with the non-infection group, the level of CSF glucose (t = 4.113, p < 0.001) was significantly lower, and the level of CSF lactic acid (t = 6.651, p < 0.001) was significantly higher in the infection group. Multivariate logistic regression analysis showed that preoperative cerebrospinal fluid glucose < 2.8 mmol/L (OR = 3.911, 95% CI: 1.653~9.253, p = 0.002) and cerebrospinal fluid lactate >2.8 mmol/L (OR = 4.712, 95% CI: 1.892~11.734, p = 0.001) are risk factors for infection after ventriculoperitoneal shunt. ROC analysis revealed that the area under the curve (AUC) for CSF glucose and lactic acid level were 0.602 (95% CI: 0.492-0.713) and 0.818 (95% CI: 0.738-0.898), respectively. The infection group had higher rates of fever and body temperature on postoperative day 3-7 (p < 0.05).

Conclusions

For adult hydrocephalus patients without clinical manifestations of intracranial infection but only with simple abnormality of cerebrospinal fluid, when the content of glucose in cerebrospinal fluid is < 2.8 mmol/L, and the content of lactic acid is >2.8 mmol/L, it is recommended to perform ventriculoperitoneal shunt after further improvement of cerebrospinal fluid indicators, otherwise, hasty operation will increase the postoperative infection rate. The postoperative fever rate of ventriculoperitoneal shunt surgery is high and the body temperature drops rapidly. If there is still fever after day 3 after surgery, whether there is intracranial infection should be considered.

Development of the Cerebrospinal Fluid in Early Stage after Hemorrhage in the Central Nervous System

Extravasation of blood in the central nervous system (CNS) represents a very strong damaged associated molecular patterns (DAMP) which is followed by rapid inflammation and can participate in worse outcome of patients. We analyzed cerebrospinal fluid (CSF) from 139 patients after the CNS hemorrhage. We compared 109 survivors (Glasgow Outcome Score (GOS) 5-3) and 30 patients with poor outcomes (GOS 2-1). Statistical evaluations were performed using the Wilcoxon signed-rank test and the Mann–Whitney U test. Almost the same numbers of erythrocytes in both subgroups appeared in days 0–3 (p = 0.927) and a significant increase in patients with GOS 2-1 in days 7–10 after the hemorrhage (p = 0.004) revealed persistence of extravascular blood in the CNS as an adverse factor. We assess 43.3% of patients with GOS 2-1 and only 27.5% of patients with GOS 5-3 with low values of the coefficient of energy balance (KEB < 15.0) in days 0–3 after the hemorrhage as a trend to immediate intensive inflammation in the CNS of patients with poor outcomes. We consider significantly higher concentration of total protein of patients with GOS 2-1 in days 0–3 after hemorrhage (p = 0.008) as the evidence of immediate simultaneously manifested intensive inflammation, swelling of the brain and elevation of intracranial pressure.

Is cerebrospinal fluid lactate useful in differentiating scrub typhus meningitis from aseptic, bacterial and tuberculous meningitis?

Scrub typhus is one of the most common causes of meningo-encephalitis in endemic areas of the Indian subcontinent. Numerous studies have established the reliability of cerebrospinal fluid lactate for differentiation of bacterial meningitis from aseptic meningitis. However, there are no reported data on the predictive value of cerebrospinal fluid lactate in scrub typhus meningitis. We thus conducted a cross-sectional study to examine the diagnostic accuracy of cerebrospinal fluid lactate in the differentiation of different causes of acute meningitis. Over two years, we studied 119 patients, with almost equal gender distribution, whose mean age was 43.58 (±18) years and their overall mean duration of fever was 11.7 (±21.0) days. Commonest clinical features overall were neck stiffness; values of cerebrospinal fluid lactate were lowest in aseptic meningitis, followed by scrub typhus, TB and bacterial meningitis. We conclude that cerebrospinal fluid lactate levels may be a useful adjunct to clinical features and laboratory investigations to differentiate between bacterial, viral, tubercular and scrub meningitis.

Diagnostic accuracy of cerebrospinal fluid lactate in confirmed cases of acute bacterial meningitis in children

Objective:

To determine the diagnostic accuracy of cerebrospinal fluid lactate level in confirmed cases of acute bacterial meningitis in children

Methods:

This cross sectional study was conducted in the Department of Paediatrics, King Edward Medical University/ Mayo Hospital, Lahore from January to December 2018. A total of 250 children, between two months - 12 years of age, of both the genders, with suspected acute bacterial meningitis were included by non-probability consecutive sampling. Each child was subjected to lumbar puncture for biochemistry, cytology, culture, and lactate level. CSF lactate level of 1.1-2.4 mmol/L was taken as normal, and >2.4 mmol/L was taken as cut off for acute bacterial meningitis. All collected data was entered and analyzed in SPSS version 22. A 2 x 2 table was made to calculate diagnostic accuracy, sensitivity, specificity, positive and negative predictive value for CSF Lactate.

Results:

The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CSF lactate taking CSF culture as gold standard was 100%, 60.61%, 17.27%, 100% and 63.6% respectively, with kappa of 0.19 and p value of 0.000.

Conclusion:

At a cut off value of 2.4 mmol/L, cerebrospinal fluid lactate level has a high diagnostic accuracy for acute bacterial meningitis.

A 2020 review on the role of procalcitonin in different clinical settings: an update conducted with the tools of the Evidence Based Laboratory Medicine

Biomarkers to guide antibiotic treatment decisions have been proposed as an effective way to enhancing a more appropriate use of antibiotics. As a biomarker, procalcitonin (PCT) has been found to have good specificity to distinguish bacterial from non-bacterial inflammations. Decisions regarding antibiotic use in an individual patient are complex and should be based on the pre-test probability for bacterial infection, the severity of presentation and the results of PCT serum concentration. In the context of a high pre-test probability for bacterial infections and/or a high-risk patient with sepsis, monitoring of PCT over time helps to track the resolution of infection and decisions regarding early stop of antibiotic treatment. As outlined by the Evidence Based Laboratory Medicine (EBLM), not only the pre-test probability but also the positive likelihood ratio influence the performance of a test do be really diagnostic. This aspect should be taken into account in the interpretation of the results of clinical trials evaluating the performance of PCT in guiding antibiotic therapy.

L-lactate in cerebrospinal fluid can be used as a biomarker of encephalitis in cattle

Cerebrospinal fluid (CSF) changes are significant for antemortem diagnoses of some neurological diseases. The aim of this study was to evaluate if the concentration of L-lactate in CSF could be used to differentiate healthy from encephalitic cattle. Cerebrospinal fluid samples from healthy cattle (n = 10) and from those naturally affected by rabies (n = 15), bovine herpesvirus type 5 meningoencephalitis (n = 16), histophilosis (n = 6), or bacterial encephalitis (n = 4), including 1 case of listeriosis, were collected and analyzed. Physical, biochemical (i.e., protein and glucose), and cellular analyses were performed in fresh samples. L-lactate, electrolytes (sodium, potassium, and chloride), calcium, and magnesium concentrations were measured in CSF samples that were kept frozen. L-lactate concentrations were also measured in plasma. Analysis of variance was used for comparison between groups and receiver operating characteristic analysis was performed considering L-lactate in CSF of healthy versus encephalitic cattle. The CSF L-lactate concentration was significantly higher in cattle with bacterial encephalitis than in healthy cattle; however, it did not differ between viral and bacterial encephalitis. The calcium concentrations were lower in cattle with encephalitis. L-lactate concentration in CSF > 3.6 mmol/L can be accepted as a cut-off value to indicate encephalitis. Thus, L-lactate in CSF is important for the diagnosis of encephalitis in cattle. Despite the small number of cases of bacterial encephalitis, it is suggested that L-lactate was not important for the differentiation between viral and bacterial encephalitis. Additional studies with a greater number of observations are necessary to clarify this, specifically in cases of listeriosis.

The Impact of Serum Glucose on the Predictive Value of Serum Lactate for Hospital Mortality in Critically Ill Surgical Patients

Background

Lactate has been widely used as a risk indicator of outcomes in critically ill patients due to its ready measurement and good predictive ability. However, the interconnections between lactate metabolism and glucose metabolism have not been sufficiently explored, yet. In this study, we aimed to investigate whether glucose levels could influence the predictive ability of lactate and design a more comprehensive strategy to assess the in-hospital mortality of critically ill patients.

Methods

We analyzed the clinical data of 293 critically ill patients. The primary outcome was in-hospital mortality. The logistic regression analysis and the area under the receiver operating characteristic curve (AUROC) were applied to evaluate the predictive ability of lactate in association with glucose.

Results

The lactate level showed significant association with in-hospital mortality, and its predictive ability was also comparable to other prognostic scores such as the SOFA score and APACHE II score. We further divided 293 patients into three groups based on glucose levels: low-glucose group (<7 mmol/L), medium-glucose group (7-9 mmol/L), and high-glucose group (>9 mmol/L). The lactate level was associated with in-hospital mortality in the low- and high- glucose groups, but not in the medium-glucose group, whereas the SOFA score and APACHE II score were associated with in-hospital mortality in all three glucose groups. The AUROC of lactate in the medium-glucose group was also the lowest among the three glucose groups, indicating a decrease in its predictive ability.

Conclusions

Our findings demonstrated that the predictive ability of lactate to assess in-hospital mortality could be influenced by glucose levels. In the medium glucose level (i.e., 7-9 mmol/L), lactate was inadequate to predict in-hospital mortality and the SOFA score; the APACHE II score should be utilized as a complementation in order to obtain a more accurate prediction.

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

OBJECTIVE

To assess the diagnostic efficiency of cerebrospinal fluid markers of procalcitonin, lactate, and cerebrospinal fluid/serum lactate ratio for detecting bacterial meningitis during traumatic lumbar puncture, and to compare these markers with routinely used uncorrected and corrected leukocyte measurements.

METHODS

Infants aged ≤90 days with traumatic lumbar puncture were prospectively studied. The diagnostic characteristics of cerebrospinal fluid assays of uncorrected and corrected leukocyte count, procalcitonin, lactate, and lactate ratio were described and compared.

RESULTS

Considering the area under the curve (95% CI) analysis and standard cutoff values, the lactate-ratio (0.985 [0.964-0.989] at cutoff 1.2) had the best test indexes for identifying meningitis, followed by lactate (0.964 [0.945-0.984] at cutoff 2.2 mmol/L) and procalcitonin (0.939 [0.891-0.986] at cutoff 0.33 ng/mL) measurement, whereas the corrected total leukocyte count assay (0.906 [0.850-0.962] at cutoff 350 cells/mm³) had diagnostic properties moderately superior to uncorrected total leukocyte count measurement (0.870 [0.798-0.943] at cutoff 430 cells/mm³).

CONCLUSION

Cerebrospinal fluid levels of procalcitonin, lactate, and lactate-ratio are reliable markers to diagnose bacterial meningitis in blood-contaminated cerebrospinal fluid.

Cerebrospinal fluid lactate: a differential biomarker for bacterial and viral meningitis in children

OBJECTIVE

To assess the performance of cerebrospinal fluid (CSF) lactate as a biomarker to differentiate bacterial meningitis from viral meningitis in children, and to define an optimal CSF lactate concentration that can be called significant for the differentiation.

METHODS

Children with clinical findings compatible with meningitis were studied. CSF lactate and other conventional CSF parameters were recorded.

RESULTS

At a cut-off value of 3mmol/L, CSF lactate had a sensitivity of 0.90, specificity of 1.0, positive predictive value of 1.0, and negative predictive value of 0.963, with an accuracy of 0.972. The positive and negative likelihood ratios were 23.6 and 0.1, respectively. When comparing between bacterial and viral meningitis, the area under the curve for CSF lactate was 0.979.

CONCLUSIONS

The authors concluded that CSF lactate has high sensitivity and specificity in differentiating bacterial from viral meningitis. While at a cut-off value of 3mmol/L, CSF lactate has high diagnostic accuracy for bacterial meningitis, mean levels in viral meningitis remain essentially below 2mmol/L.

USE OF SCORE AND CEREBROSPINAL FLUID LACTATE DOSAGE IN DIFFERENTIAL DIAGNOSIS OF BACTERIAL AND ASEPTIC MENINGITIS

Objective:

To evaluate Bacterial Meningitis Score (BMS) on its own and in association with Cerebrospinal Fluid (CSF) lactate dosage in order to distinguish bacterial from aseptic meningitis.

Methods:

Children diagnosed with meningitis at a tertiary hospital between January/2011 and December/2014 were selected. All data were obtained upon admission. BMS was applied and included: CSF Gram staining (2 points); CSF neutrophil count ≥1,000 cells/mm³ (1 point); CSF protein ≥80 mg/dL (1 point); peripheral blood neutrophil count ≥10,000 cells/mm³ (1 point) and seizures upon/before arrival (1 point). Cutoff value for CSF lactate was ≥30 mg/dL. Sensitivity, specificity and negative predictive value of several BMS cutoffs and BMS associated with high CSF lactate were evaluated for prediction of bacterial meningitis.

Results:

Among 439 eligible patients, 94 did not have all data available to complete the score, and 345 patients were included: 7 in bacterial meningitis group and 338 in aseptic meningitis group. As predictive factors of bacterial meningitis, BMS ≥1 had 100% sensitivity (95%CI 47.3-100), 64.2% specificity (58.8-100) and 100% negative predictive value (97.5-100); BMS ≥2 or BMS ≥1 associated with high CSF lactate also showed 100% sensitivity (47.3-100); but 98.5% specificity (96.6-99.5) and 100% negative predictive value (98.3-100).

Conclusions:

2 point BMS in association with CSF lactate dosage had the same sensitivity and negative predictive value, with increased specificity for diagnosis of bacterial meningitis when compared with 1-point BMS.

Diagnostic value of lactate, procalcitonin, ferritin, serum-C-reactive protein, and other biomarkers in bacterial and viral meningitis: A cross-sectional study

There are many difficulties distinguishing bacterial from viral meningitis that could be reasonably solved using biomarkers. The aim of this study was to evaluate lactate, procalcitonin (PCT), ferritin, serum-CRP (C-reactive protein), and other known biomarkers in differentiating bacterial meningitis from viral meningitis in children.All children aged 28 days to 14 years with suspected meningitis who were admitted to Mofid Children's Hospital, Tehran, between October 2012 and November 2013, were enrolled in this prospective cross-sectional study. Children were divided into 2 groups of bacterial and viral meningitis, based on the results of cerebrospinal fluid (CSF) culture, polymerase chain reaction, and cytochemical profile. Diagnostic values of CSF parameters (ferritin, PCT, absolute neutrophil count [ANC], white blood cell count, and lactate) and serum parameters (PCT, ferritin, CRP, and erythrocyte sedimentation rate [ESR]) were evaluated.Among 50 patients with meningitis, 12 were diagnosed with bacterial meningitis. Concentrations of all markers were significantly different between bacterial and viral meningitis, except for serum (P = .389) and CSF (P = .136) PCT. The best rates of area under the receiver operating characteristic (ROC) curve (AUC) were achieved by lactate (AUC = 0.923) and serum-CRP (AUC = 0.889). The best negative predictive values (NPV) for bacterial meningitis were attained by ANC (100%) and lactate (97.1%).The results of our study suggest that ferritin and PCT are not strong predictive biomarkers. A combination of low CSF lactate, ANC, ESR, and serum-CRP could reasonably rule out the bacterial meningitis.

Usefulness of blood and cerebrospinal fluid laboratory testing to predict bacterial meningitis in the emergency department

INTRODUCTION

The classic clinical presentation of bacterial meningitis (BM) is observed in less than half of the cases in adults, and symptoms are less specific in children, the elderly or immunocompromised, and other chronic patients. The usual signs and symptoms do not provide optimal sensitivity and specificity for distinguishing possible BM from viral meningitis (VM), which may lead to a delay in the appropriate antimicrobial therapy. Society therefore stands to benefit from the development of effective, objective, and rapid tools able to predict and identify patients with BM. These tools include laboratory tests for blood and cerebrospinal fluid (CSF). The aim of this review is to summarise recently published scientific evidence in order to clarify existing controversies and compare the usefulness and diagnostic ability of the different parameters used to predict BM.

DEVELOPMENT

Systematic search of the main bibliographic databases and platforms to identify articles published between January 2000 and January 2016. We selected 59 articles that meet the objectives of this review.

CONCLUSIONS

CSF lactate, proportion of polymorphonuclear leukocytes, and CSF glucose, as well as serum procalcitonin (PCT), are the independent factors most predictive of bacterial aetiology. The model that combines serum PCT and CSF lactate achieves the highest predictive power for BM, with a sensitivity and specificity exceeding 99%. We should consider BM when CSF lactate >33 md/dL and/or PCT>0.25ng/mL.

Diagnostic Accuracy of Procalcitonin in Bacterial Meningitis Versus Nonbacterial Meningitis: A Systematic Review and Meta-Analysis

Several studies have investigated the diagnostic accuracy of procalcitonin (PCT) levels in blood or cerebrospinal fluid (CSF) in bacterial meningitis (BM), but the results were heterogeneous. The aim of the present study was to ascertain the diagnostic accuracy of PCT as a marker for BM detection. A systematic search of the EMBASE, Scopus, Web of Science, and PubMed databases was performed to identify studies published before December 7, 2015 investigating the diagnostic accuracy of PCT for BM. The quality of the eligible studies was assessed using the revised Quality Assessment for Studies of Diagnostic Accuracy method. The overall diagnostic accuracy of PCT detection in CSF or blood was pooled using the bivariate model. Twenty-two studies involving 2058 subjects were included in this systematic review and meta-analysis. The overall specificities and sensitivities were 0.86 and 0.80 for CSF PCT, and 0.97 and 0.95 for blood PCT, respectively. Areas under the summary receiver operating characteristic curves were 0.90 and 0.98 for CSF PCT and blood PCT, respectively. The major limitation of this systematic review and meta-analysis was the small number of studies included and the heterogeneous diagnostic thresholds adopted by eligible studies. Our meta-analysis shows that PCT is a useful biomarker for BM diagnosis.

Tuberculous meningitis: advances in diagnosis and treatment

INTRODUCTION

Tuberculous meningitis (TBM) is the most severe form of infection caused by Mycobacterium tuberculosis, causing death or disability in more than half of those affected. The aim of this review is to examine recent advances in our understanding of TBM, focussing on the diagnosis and treatment of this devastating condition.

SOURCES OF DATA

Papers on TBM published between 1891 and 2014 and indexed in the NCBI Pubmed. The following search terms were used: TBM, diagnosis, treatment and outcome.

AREAS OF AGREEMENT

The diagnosis of TBM remains difficult as its presentation is non-specific and may mimic other causes of chronic meningoencephalitis. Rapid recognition of TBM is crucial, however, as delays in initiating treatment are associated with poor outcome. The laboratory diagnosis of TBM is hampered by the low sensitivity of cerebrospinal fluid microscopy and the slow growth of M. tuberculosis in conventional culture systems. The current therapy of TBM is based on the treatment of pulmonary tuberculosis, which may not be ideal. The combination of TBM and HIV infection poses additional management challenges because of the need to treat both infections and the complications associated with them.

AREAS OF CONTROVERSY

The pathogenesis of TBM remains incompletely understood limiting the development of interventions to improve outcome. The optimal therapy of TBM has not been established in clinical trials, and increasing antimicrobial resistance threatens successful treatment of this condition. The use of adjunctive anti-inflammatory agents remains controversial, and their mechanism of action remains incompletely understood. The role of surgical intervention is uncertain and may not be available in areas where TBM is common.

GROWING POINTS

Laboratory methods to improve the rapid diagnosis of TBM are urgently required. Clinical trials of examining the use of high-dose rifampicin and/or fluoroquinolones are likely to report in the near future.

AREAS TIMELY FOR DEVELOPING RESEARCH

The use of biomarkers to improve the rapid diagnosis of TBM warrants further investigation. The role of novel antituberculosis drugs, such as bedaquiline and PA-824, in the treatment of TBM remains to be explored. Human genetic polymorphisms may explain the heterogeneity of response to anti-inflammatory therapies and could potentially be used to tailor therapy.

Spectrum of complicated migraine in children: A common profile in aid to clinical diagnosis

Complicated migraine encompasses several individual clinical syndromes of migraine. Such a syndrome in children frequently presents with various neurological symptoms in the Emergency Department. An acute presentation in the absence of headache presents a diagnostic challenge. A delay in diagnosis and treatment may have medicolegal implication. To date, there are no reports of a common clinical profile proposed in making a clinical diagnosis for the complicated migraine. In this clinical review, we propose and describe: (1) A common clinical profile in aid to clinical diagnosis for spectrum of complicated migraine; (2) How it can be used in differentiating complicated migraine from migraine without aura, migraine with aura, and seizure; (3) We discuss the status of complicated migraine in the International Headache Society classification 2013; and (4) In addition, a common treatment strategy for the spectrum of migraine has been described. To diagnose complicated migraine clinically, it is imperative to adhere with the proposed profile. This will optimize the use of investigation and will also avoid a legal implication of delay in their management. The proposed common clinical profile is incongruent with the International Headache Society 2013. Future classification should minimize the dissociation from clinically encountered syndromes and coin a single word to address collectively this subtype of migraine with an acute presentation of a common clinical profile.

The diagnostic value of cerebrospinal fluids procalcitonin and lactate for the differential diagnosis of post-neurosurgical bacterial meningitis and aseptic meningitis

OBJECTIVES

Distinguishing between post-neurosurgical bacterial meningitis (PNBM) and aseptic meningitis is difficult. This study aims to evaluate the combined diagnostic value of CSF procalcitonin and lactate as novel PNBM markers in hospitalized post-neurosurgery patients.

DESIGN AND METHODS

This study was performed using CSF samples, collected by lumbar puncture, from 178 PNBM-suspected patients enrolled in a retrospective clinical study. The levels of CSF procalcitonin and lactate were appropriately assayed and the combined diagnostic value of these markers was assessed using receiver operating characteristic (ROC) curves, a two by two table, and non-parametric tests.

RESULTS

Fifty of the 178 patients were diagnosed with PNBM, based on the clinical symptoms and laboratory results. These PNBM patients showed significantly elevated levels of CSF procalcitonin and CSF lactate compared with the non-PNBM group (p<0.001 for both). It was revealed that the cut-off values for the diagnosis of PNBM were: 0.075ng/mL (sensitivity, 68%; specificity, 73%) for procalcitonin and 3.45mmol/L (sensitivity, 90%; specificity, 85%) for lactate. A serial test combining the levels of these two markers showed decreased sensitivity (64%) and increased specificity (91%), compared with either marker alone. In contrast, a parallel test combining the levels of these both markers showed increased sensitivity (96%) and decreased specificity (65%), compared with either marker alone.

CONCLUSION

Our study shows that the combined use of CSF procalcitonin and lactate can reliably distinguish between PNBM and non-PNBM and can be included in the design of diagnostic approaches to circumvent the shortcomings of conventional methods.