Cristina Prat

Comparison of Two Commercially Available Gamma Interferon Blood Tests for Immunodiagnosis of Tuberculosis

ABSTRACT We evaluated the T-SPOT.TB and Quantiferon-TB Gold In tube (QFN-G-IT) tests for diagnosing Mycobacterium tuberculosis infection. T-SPOT.TB was more sensitive than QFN-G-IT in diagnosing both active and latent infection. Both gamma interferon tests were unaffected by prior Mycobacterium bovis BCG vaccination. Among children who were not BCG vaccinated but had a positive tuberculin skin test, QFN-G-IT was negative in 53.3% of cases, and T-SPOT.TB was negative in 50% of cases.

Serum Procalcitonin Level and Other Biological Markers to Distinguish Between Bacterial and Aseptic Meningitis in Children: A European Multicenter Case Cohort Study

OBJECTIVE To validate procalcitonin (PCT) level as the best biological marker to distinguish between bacterial and aseptic meningitis in children in the emergency department. DESIGN Secondary analysis of retrospective multicenter hospital-based cohort studies. SETTING Six pediatric emergency or intensive care units of tertiary care centers in 5 European countries. PARTICIPANTS Consecutive children aged 29 days to 18 years with acute meningitis. MAIN OUTCOME MEASURES Univariate analysis and meta-analysis to compare the performance of blood parameters (PCT level, C-reactive protein level, white blood cell count, and neutrophil count) and cerebrospinal fluid parameters (protein level, glucose level, white blood cell count, and neutrophil count) quickly available in the emergency department to distinguish early on between bacterial and aseptic meningitis. RESULTS Of 198 patients analyzed, 96 had bacterial meningitis. Sensitivity of cerebrospinal fluid Gram staining was 75%. The PCT level had significantly better results than the other markers for area under the receiver operating characteristic curve (0.98; 95% confidence interval, 0.95-0.99; P = .001). At a 0.5-ng/mL threshold, PCT level had 99% sensitivity (95% confidence interval, 97%-100%) and 83% specificity (95% confidence interval, 76%-90%) for distinguishing between bacterial and aseptic meningitis. The diagnostic odds ratio between high PCT level and bacterial meningitis was 139 (95% confidence interval, 39-498), without significant heterogeneity between centers. CONCLUSIONS The PCT level is a strong predictor for distinguishing between bacterial and aseptic meningitis in children in the emergency department. Its combination with other parameters in an effective clinical decision rule could be helpful.

Procalcitonin, C-reactive protein and leukocyte count in children with lower respiratory tract infection

Background. Lower respiratory tract infection is the most common infection leading to unnecessary antibiotic treatment in children. Etiologic diagnosis is not immediately achieved, and the pathogen remains unidentified in a large number of cases. Neither clinical nor laboratory factors allow for a rapid distinction between bacterial and viral etiology. The aim of our study was to evaluate the reliability of procalcitonin (PCT), C-reactive protein (CRP) and leukocyte count in distinguishing pneumococcal, atypical and viral lower respiratory tract infection. Methods. PCT, CRP and leukocyte count were measured in children with microbiologically documented diagnoses of lower respiratory tract infection. The results were compared of children with pneumococcal, atypical and viral etiologies. Results. PCT and CRP showed significant correlation with a bacterial etiology of lower respiratory tract infection. No significance was found for leukocyte count. Using a cutoff point of 2 ng/ml for PCT and 65 mg/l for CRP, the sensitivities and specificities for distinguishing bacterial from viral lower respiratory tract infections were 68.6 and 79.4% for PCT and 79.1 and 67.1% for CRP. The sensitivities and specificities for distinguishing pneumococcal from other etiologies were 90.3 and 74.1% for PCT and 90.3 and 60% for CRP, respectively. Conclusions. High PCT and CRP values show a significant correlation with the bacterial etiology of lower respiratory tract infection. PCT and CRP show good sensitivity for distinguishing pneumococcal from other etiologies. PCT shows higher specificity than CRP. PCT and CRP can help make decisions about antibiotic therapy in children with lower respiratory tract infections.

Evaluation of procalcitonin, neopterin, C-reactive protein, IL-6 and IL-8 as a diagnostic marker of infection in patients with febrile neutropenia.

Infectious complications in neutropenic patients are a major cause of morbidity and mortality. Clinical signs are unspecific and fever can be attributed to other causes. Inflammatory biomarkers have emerged as potentially useful in diagnosis of bacterial and fungal infection. Levels of several biomarkers were measured in patients with hematological malignancy at diagnosis and at the beginning of neutropenia due to cytostatic treatment or after hematopoietic stem cell transplantation, and daily until 6 days after presenting fever. Procalcitonin (PCT) and neopterin levels were not elevated at diagnosis or at the beginning of neutropenia. C-reactive protein (CRP) was moderately elevated. PCT levels were significantly higher in patients with Gram-negative bacteremia at 24–48 h after the onset of fever. Patients with probable fungal infection presented elevated PCT values when fever persisted for more than 4–5 days. CRP was more sensitive to predict bacteremia (both Gram-positive and Gram-negative) but the specificity was low. Neither neopterin, IL-6 nor IL-8 presented significant differences according to the origin or etiology of fever. Since it showed a high negative predictive value of Gram-negative bacteremia, clinical prediction rules that attempt to predict a high risk of severe infection might be improved by including measurement of PCT.

Usefulness of Urinary Antigen Detection by an Immunochromatographic Test for Diagnosis of Pneumococcal Pneumonia in Children

ABSTRACT We evaluated an immunochromatographic assay detecting pneumococcal antigen in urine samples from children diagnosed with pneumococcal pneumonia. The sensitivity and specificity of the immunochromatographic test with nonconcentrated urine (NCU) were 86.7 and 62.9%, respectively; with concentrated urine (CU), they were 100 and 11.7%, respectively. Pneumococcal antigen was also detected in 42.5% of NCU and 87.1% of CU samples from nasopharyngeal carriers. This is a nonspecific test for the diagnosis of pneumococcal pneumonia in children, particularly the very young.

GenoType MTBDRplus Assay for Molecular Detection of Rifampin and Isoniazid Resistance in Mycobacterium tuberculosis Strains and Clinical Samples

ABSTRACT The purpose of this study was to evaluate the GenoType MTBDRplus assay (Hain Lifescience GmbH, Nehren, Germany) for its ability to detect resistance to rifampin (RIF) and isoniazid (INH) in Mycobacterium tuberculosis clinical strains and directly in clinical samples. A total of 62 clinical strains characterized with the Bactec 460TB system were included. For the INH-resistant strains, the MIC was measured and sequencing was performed. Sixty-five clinical samples from 28 patients (39 smear-positive samples and 26 smear-negative samples) were also tested directly. The corresponding isolates of the clinical specimens were studied with the Bactec 460TB system. The overall rates of concordance of the MTBDRplus assay and the Bactec 460TB system for the detection of RIF and INH susceptibility in clinical strains were 98.3% (61/62) and 79% (49/62), respectively. The rate of concordance between the Bactec 460TB system and the MTBDRplus test for the detection of INH resistance in the group of 27 strains with low-level resistance was 62.9% (17/27), and that for the detection of INH resistance in the group of 21 strains with high-level resistance was 85.71% (18/21). Valid test results were obtained for 78.45% (51/65) of the clinical samples tested. The rates of concordance between both assays for the detection of drug resistance in these samples were 98% (50/51) for RIF and 96.2% (49/51) for INH. Taking into account only one sample per patient, the overall rate of concordance between both tests was 92.85% (26/28). The GenoType MTBDRplus assay is easy to perform and is a useful tool for the management of tuberculosis, as it allows the detection of resistance to RIF and INH in M. tuberculosis strains and also in clinical samples.

Elevated serum procalcitonin values correlate with renal scarring in children with urinary tract infection.

Background. Urinary tract infection (UTI) in young children carries the risk of parenchymal damage and sequelae. The location of the infection within the urinary tract influences decisions regarding both therapeutics and follow-up. Because clinical features and laboratory markers of infection at an early age are not specific, it is difficult to make a distinction between lower UTI and acute pyelonephritis. Procalcitonin (PCT) has been studied as a marker of severe bacterial infection. The aim of this study was to test the usefulness of PCT concentration in serum to distinguish between uncomplicated UTI and severe acute pyelonephritis with renal scars. Methods. PCT was measured by immunoluminometric assay in serum samples from children with microbiologically documented infection. Severe renal involvement was assessed by 99mTc-dimercaptosuccinic acid gammagraphy done 5 to 6 months after the episode to check for the presence of parenchymal scars. C-reactive protein (CRP) and leukocyte count were also measured. Results. PCT at presentation showed a significant correlation (P < 0.001) with the presence of renal scars in children with UTI. Using a cutoff of 1 ng/ml for PCT and 20 mg/l for CRP, sensitivity and specificity in distinguishing between urinary tract infection with and without renal damage were 92.3 and 61.9%, respectively, for PCT and 92.3 and 34.4% for CRP. Positive and negative predictive values were 32 and 97.5%, respectively, for PCT and 23 and 95%, respectively, for CRP. Conclusions. A low PCT value at admission indicates a low risk of long term renal scarring. Increased PCT values at admission correlate with the presence of scars. PCT values have proved to be more specific than CRP and leukocyte count for identifying patients who might develop renal damage.

T-cell responses to the Mycobacterium tuberculosis-specific antigens in active tuberculosis patients at the beginning, during, and after antituberculosis treatment.

The objectives of the study were to assess the performance of the QuantiFERON-TB Gold In-Tube (QFN-G-IT) and the T-SPOT.TB tests in the immunodiagnosis of active tuberculosis (TB) in adult patients, and to study the T-cell interferon gamma (IFN-gamma) responses during treatment and in patients who have recovered after curative treatment and self-healed TB patients. When only analyzing patients included at the beginning of treatment, the sensitivity was 83.3% for T-SPOT.TB and 69.4% for QFN-G-IT. In contrast, when evaluating patients during treatment, the sensitivity of the T-SPOT.TB and QFN-G-IT decreased to 69.8% and 48.8%, respectively. The response to the specific antigens increased after finishing the treatment compared with the values during the treatment. The T-SPOT.TB was more sensitive in diagnosing active TB than the QFN-G-IT. The IFN-gamma tests could be used as a complementary method in the diagnosis of active TB.

Distinguishing between bacterial and aseptic meningitis in children: European comparison of two clinical decision rules

Background Clinical decision rules (CDRs) could be helpful to safely distinguish between bacterial and aseptic meningitis (AM). Objective To compare the performance of two of these CDRs for children: the Bacterial Meningitis Score (BMS) and the Meningitest. Design Secondary analysis of retrospective multicentre hospital-based cohort study. Setting Six paediatric emergency or intensive care units of tertiary care centres in five European countries. Patients Consecutive children aged 29 days to 18 years presenting with acute meningitis and procalcitonin (PCT) measurement. Intervention None. Main outcome measures The sensitivity and specificity of the BMS (start antibiotics in case of seizure, positive cerebrospinal fluid (CSF) Gram staining, blood neutrophil count ≥10 ×109/l, CSF protein level ≥80 mg/dl or CSF neutrophil count ≥1000 ×106/l) and the Meningitest (start antibiotics in case of seizure, purpura, toxic appearance, PCT level ≥0.5 ng/ml, positive CSF Gram staining or CSF protein level ≥50 mg/dl) were compared using a McNemar test. Results 198 patients (mean age 4.8 years) from six centres in five European countries were included; 96 had bacterial meningitis. The BMS and Meningitest both showed 100% sensitivity (95% CI 96% to 100%). The BMS had a significantly higher specificity (52%, 95% CI 42% to 62% vs 36%, 95% CI 27% to 46%; p<10−8). Conclusion The Meningitest and the BMS were both 100% sensitive. This result provides level II evidence for the sensitivity of both rules, which can be used cautiously. However, use of the BMS could safely avoid significantly more unnecessary antibiotic treatments for children with AM than can the Meningitest in this population.

Use of Quantitative and Semiquantitative Procalcitonin Measurements to Identify Children with Sepsis and Meningitis

During infancy and childhood, clinical signs of infection and conventional laboratory markers are not specific in the early phase of disease [1]. The availability of a parameter that more rapidly identifies children suspected to have bacterial sepsis before microbiological results are available would minimize unnecessary treatments and hospitalization. Since its original description, the importance of procalcitonin (PCT) as an indicator of systemic bacterial infection has been demonstrated in many reports [2, 3, 4, 5]. The aim of our study was to evaluate the reliability of PCT measurement by quantitative luminometric immunoassay (LIA) in distinguishing between systemic bacterial infection (sepsis and/or meningitis), localized bacterial infection and aseptic meningitis in children, compared to leukocyte count and C-reactive protein (CRP) levels. We also evaluated the correlation of a rapid immunochromatographic test (ICT) for semiquantitative PCT measurement in comparison with quantitative test results. The study was carried out on selected children aged between 1 month and 12 years who were admitted to the pediatric emergency department of our hospital after presenting with fever of less than 12-h duration. At the time of admission, blood samples were collected for leukocyte count, CRP and PCT measurement. Clinical specimens were collected for microbiological testing in order to correctly establish the etiology. Serial serum samples for PCT and CRP assays were collected daily when possible. Patients were grouped retrospectively according to the type of illness. Group 1 included 25 children diagnosed with bacterial sepsis and/or meningitis by culture of blood and/or cerebrospinal fluid (CSF) samples: Neisseria meningitidis was isolated in 18 cases, Streptococcus pneumoniae in 6 and Haemophilus influenzae in 1. Bacteria were isolated from CSF culture only in 8 patients, blood culture only in 10 and both culture types in 7. Group 2 included 18 children diagnosed with aseptic meningitis by compatible clinical presentation, negative Gram stain, cultures and antigen tests for bacterial infection using blood and CSF samples, compatible CSF analysis (pleocytosis with a predominance of mononuclear cells) and successful recovery without antibiotic therapy. Viral cultures were not performed. Group 3 included 22 children presenting with localized bacterial infection such as purulent conjunctivitis, acute otitis media, streptococcal pharyngitis, cellulitis or sinusitis, confirmed by culture of the site of infection and negative blood cultures. The bacteria isolated were Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes. In order to establish normal PCT levels for comparison, serum samples were also collected from a control group of 25 similarly aged healthy children admitted to the hospital for elective surgery. PCT was measured using LIA (Lumitest PCT; Brahms Diagnostica, Germany) for quantitative detection and ICT (PCT-Q; Brahms Diagnostica) for semiquantitative detection following the manufacturer’s instructions. LIA requires 20 l of serum and 90–120 min to be performed. ICT requires 200 l of serum and results can be obtained in 30 min; samples can be measured individually. CRP was measured using a turbidimetric assay (C-Reactive Protein FlexT reagent cartridge, Dimension; Dade Behring, USA) and leukocyte count was measured with Coulter Counter Maxm (Coulter, USA). Comparison between groups for quantitative parameters was performed using the non-parametric MannWhitney U test for CRP, leukocyte count and PCT. Diagnostic accuracy and optimum cut-off points were determined using a receiver operating characteristic curve. Comparisons between the two methods were made C. Prat ()) · J. Dom nguez · M. Gim nez · S. Blanco · V. Ausina Servei de Microbiologia, Hospital Universitari Germans Trias i Pujol, C/Canyet s/n, 08916 Badalona, Spain e-mail: crisprat@ns.hugtip.scs.es Tel.: +34-93-4978894 Fax: +34-93-4978895