Enhanced versus automated urinalysis for screening of urinary tract infections in children in the emergency department.

BACKGROUND: Urinary tract infections (UTI) are the most common serious bacterial infection in febrile infants. Urinalysis (UA) is a screening test for preliminary diagnosis of UTI. UA can be performed manually or using automated techniques. We sought to compare manual versus automated UA for urine specimens obtained via catheterization in the pediatric emergency department. METHODS: In this prospective study, we processed catheterized urine samples from infants with suspected UTI by both the manual method (enhanced UA) and the automated method. We defined a positive enhanced UA as ≥ 10 white blood cells per cubic millimeter and presence of any bacteria per 10 oil immersion fields on a Gram-stained smear. We defined a positive automated UA as ≥ 2 white blood cells per high-powered field and presence of any bacteria using the IRIS iQ200 ELITE. We defined a positive urine culture as growth of ≥ 50,000 colony-forming units per milliliter of a single uropathogen. We analyzed data using SPSS software. RESULTS: A total of 703 specimens were analyzed. Prevalence of UTI was 7%. For pyuria, the sensitivity and positive predictive value (PPV) of the enhanced UA in predicting positive urine culture were 83.6% and 52.5%, respectively; corresponding values for the automated UA were 79.5% and 37.5%, respectively. For bacteriuria, the sensitivity and PPV of a Gram-stained smear (enhanced UA) were 83.6% and 59.4%, respectively; corresponding values for the automated UA were 73.4%, and 26.2%, respectively. Using criteria of both pyuria and bacteriuria for the enhanced UA resulted in a sensitivity of 77.5% and a PPV of 84.4%; corresponding values for the automated UA were 63.2% and 51.6%, respectively. Combining automated pyuria (≥ 2 white blood cells/high-powered microscopic field) with a Gram-stained smear resulted in a sensitivity of 75.5% and a PPV of 84%. CONCLUSIONS: Automated UA is comparable with manual UA for detection of pyuria in young children with suspected UTI. Bacteriuria detected by automated UA is less sensitive and specific for UTI when compared with a Gram-stained smear. We recommend using either manual or automated measurement of pyuria in combination with Gram-stained smear as the preferred technique for UA of catheterized specimens obtained from children in an acute care setting.

Comparison of CEDIA FK506 assay with HPLC/MS/MS in a large cohort of pediatric patients.

FK506 (tacrolimus), a macrolide immunosuppressant, is widely used in pediatric transplant patients, but a relatively narrow therapeutic window in children vs adults requires close and accurate monitoring of whole blood FK506 levels. High-pressure liquid chromatography/tandem mass spectrometry (HPLC/MS/MS)-based assays have been viewed as the gold standard but are more time and labor intensive than cloned enzyme donor immunoassay (CEDIA). To analyze differences between the 2 assays, we assayed FK506 in 348 split samples simultaneously by both methods. A further 70 samples were stratified by organ transplantation type: cardiac (13%), renal (23%), small bowel (22%), or liver transplantation (42%). Results were analyzed using standard statistical techniques for method comparison. CEDIA overestimated the FK506 value relative to HPLC/MS/MS by more than 20% in 40% of cases (139/348), whereas CEDIA underestimated the FK506 value relative to HPLC/MS/MS by more than 20% in 13.5% of cases, for a total inaccuracy of 53% using a ±20% cutoff. Only 28% of samples (99/348) measured by CEDIA were within 10% of the value obtained by HPLC/MS/MS. Bland-Altman analysis showed a mean bias of 9.5% in favor of CEDIA over HPLC/MS/MS (95% confidence interval, 6.1%-12.9%). Positive bias was greatest for liver transplant and R(2) values were lowest for intestinal transplant patients, indicating that HPLC/MS/MS may be a better option for this pediatric transplant subgroup.

Toxicology laboratory analysis and human exposure to p-chloroaniline.

INTRODUCTION: p-Chloroaniline is more potent at producing methemoglobin than aniline in animal models. This case highlights the clinical presentation of an inhalation exposure to p-chloroaniline and associated laboratory analysis. An in-vitro study evaluating the metabolism of p-chloroaniline in human hepatocytes was undertaken to evaluate the metabolic fate more closely. CASE PRESENTATION: A 20 year-old man was working at a chemical waste plant when he developed dizziness, abdominal pain, and nausea. The exam was remarkable for coma, tachycardia, cyanosis, and pulse oximetry of 75%. Arterial blood gases showed a pH 7.38, pCO(2) 41 mmHg, pO(2) 497 mmHg, bicarbonate 24 mEq/L and methemoglobin 69%. Methylene blue administration led to complete recovery without sequelae. p-Chloroaniline was later identified as the chemical involved. He denied direct contact with the chemical, but was not wearing a dust mask or respirator. GC/MS confirmed p-chloroaniline and metabolites in the patient's urine. METHODS: Human hepatocytes were incubated with 100 microM p-chloroaniline for 24 hours, in both rifampicin- and vehicle only-treated cells. The cell culture medium was collected for GC/MS analysis for p-chloroaniline metabolites. RESULTS: Similar to the patient sample, both p-chloroaniline and p-chloroacetanilide were identified by GC/MS in hepatocytes incubated with p-chloroaniline. Neither p-chloroaniline incubated in empty cell culture nor direct GC/MS injection of p-chloroaniline generated any p-chloroacetanilide via non-enzymatic degradation. DISCUSSION/CONCLUSION: The seemingly innocuous dermal and inhalation exposure to p-chloroaniline dust can lead to life-threatening methemoglobinemia. The diagnosis can be confirmed with GC/MS analysis of the patient's urine, searching for p-chloroaniline and its primary metabolite p-chloroacetanilide.

Drug monitoring: simultaneous analysis of lamotrigine, oxcarbazepine, 10-hydroxycarbazepine, and zonisamide by HPLC-UV and a rapid GC method using a nitrogen-phosphorus detector for levetiracetam.

A high-performance liquid chromatography (HPLC) assay using UV detection is described for the simultaneous measurement of the newer generation anti-epileptic medications lamotrigine, oxcarbazepine (parent drug and active metabolite 10- hydroxycarbazepine), and zonisamide. Detection of all four compounds can be done at 230 nm; however, there is a potential interference with zonisamide in patients on clonazepam therapy. Therefore, the method uses dual wavelength detection: 230 nm for oxcarbazepine and 10-hydroxycarbazepine and 270 nm for lamotrigine and zonisamide. In addition, a simple gas chromatography method using a nitrogen-phosphorus detector is described for the measurement of levetiracetam, another of the recently approved anti-epileptic medications. For both methods, limits of quantitation, linearities, accuracies, and imprecisions cover the therapeutic range for drug monitoring of patients. A wide variety of clinical drugs, including other anti-epileptic drugs, do not interfere with these assays. These procedures would be of special interest to clinical laboratories, particularly due to the limited availability of immunoassays for newer generation anti-epileptic medications and that therapeutic uses of these drugs are expanding beyond epilepsy to other neurologic and psychiatric disorders.

Simultaneous determination of lamotrigine, zonisamide, and carbamazepine in human plasma by high-performance liquid chromatography.

A high-performance liquid chromatography assay with ultraviolet detection was developed for the simultaneous determination of the anti-epileptic drugs lamotrigine, carbamazepine and zonisamide in human plasma and serum. Lamotrigine, carbamazepine, zonisamide and the internal standard chloramphenicol were extracted from serum or plasma using liquid-liquid extraction under alkaline conditions into an organic solvent. The method was linear in the range 1-30 microg/mL for lamotrigine, 2-20 microg/mL for carbamazepine, and 1-40 microg/mL for zonisamide. Within- and between-run precision studies demonstrated coefficient of variation <10% at all tested concentrations. Other anti-epileptic medications tested did not interfere with the assay. The method is appropriate for determining lamotrigine, carbamazepine and zonisamide serum or plasma concentrations for therapeutic monitoring.

Role of laboratory in the management of phenylbutazone poisoning.

We report a rare case of intentional overdose of phenylbutazone in a 15-yr-old female. The patient exhibited symptoms of phenylbutazone toxicity and the presence of the drug was confirmed by gas chromatography mass-spectrometry (GC-MS) analysis of the initial urine sample. The patient underwent plasmapheresis to remove the drug from the circulation. Semiquantitation of sequential serum samples by GC-MS revealed elimination of phenylbutazone by day 5 of admission at which time the plasmapheresis was discontinued. Elevated blood urea nitrogen (BUN) and creatinine returned to normal. Analysis of biomarkers for liver necrosis and regeneration in sequential serum samples revealed the restoration of normal liver function by day 5. This case further confirms our previous observations that biomarkers for liver necrosis and regeneration can predict the outcome of patients with liver damage due to toxins.