Urine Test Strips as a Bedside Diagnostic Aid to Rule out Blood in CSF: A Validation.

INTRODUCTION: Patients presenting to the emergency department with acute-onset, atypical headaches require an evaluation for subarachnoid hemorrhage (SAH). The standard evaluation for SAH includes noncontrast computed tomography of the head and, if negative, a lumbar puncture to determine the presence of blood in the cerebrospinal fluid (CSF). In austere environments without full laboratory capabilities, a rapid bedside diagnostic test allowing clinicians to rule out SAH would reduce costly transfers of patients requiring further evaluation. CSF samples obtained while evaluating patients for potential SAH were tested with the blood panel of Bayer Multistix urine test strips. METHODS: We compared the test strip color change to the number of red blood cells per high power field found on laboratory analysis of the CSF. RESULTS: The sensitivity of the Multistix for detecting red blood cells in the CSF was 100%, with a specificity of 56%. The positive predictive value was 37%, and the negative predictive value was 100%. CONCLUSION: These results are encouraging and may form the basis for potential use of urine test strips as a tool to rule out subarachnoid blood in austere environments, but the test strips' low specificity limits their usefulness as a practical clinical tool at this time.

Urine test strips to exclude cerebral spinal fluid blood.

INTRODUCTION: Determining the presence or absence of red blood cells (RBC) or their breakdown products in cerebrospinal fluid (CSF) is essential for the evaluation of subarachnoid hemorrhage (SAH) in headache patients. Current methodology for finding blood in the CSF is either spectrophotometric detection of pigment, which is time consuming and labor intensive, or visual assesment of samples for color change (xanthochromia), which is inaccurate. Bayer Multistix(®) urine test strips are designed to test urine for RBC by detecting the presence of hemoglobin. The aim of this pilot study was to evaluate the perfomance of urine reagent test strips for ruling out the presence of RBC in CSF. METHODS: We compared color changes on Multistix(®) urine test strips to the standard of spectrophotometric absorbtion at 415nm and initial RBC counts in 138 visually clear CSF samples. RESULTS: We performed Pearson Chi-Square and likelihood ratios on the results and found a correlation between a negative result on the urine test strip and less than 5 RBC per high power field and a spectrophotometric absorbance of less than 0.02% at 415nm in a CSF sample. CONCLUSION: These results warrant further investigation in the form of a prospective clinical validation as it may alter the emergency department evaluation for SAH.

A cellulose synthase-containing compartment moves rapidly beneath sites of secondary wall synthesis.

The woody secondary walls of plants represent the major sites of cellulose deposition. The polymerization of cellulose occurs at the plasma membrane by the secondary wall cellulose synthase complex (CSC). In the long, cylindrical cells that make up the xylem, secondary wall deposition is confined to discrete regions of the cell, and yellow fluorescent protein (YFP)-labeled CSCs are also localized to these regions. Using fluorescence loss in photobleaching (FLIP) of complete hoops containing YFP-CSCs, we demonstrate movement of the complexes beneath the nascent secondary wall in developing xylem vessels. We have devised a method for determining particle velocities for particles moving around a cylindrical object using data from FLIP. By applying this method to the hoops of YFP-CSCs of the developing vessels, we have obtained the first estimates of speed of these complexes. These speeds are calculated to be in excess of 7 microm s(-1) and are far higher than those speeds previously reported for the primary wall complex. These high speeds are unlikely to be consistent with CSC movement being attributed to cellulose synthesis alone, and suggest the existence of a highly motile compartment beneath the nascent secondary wall.