False-positive Readings Research Articles

Occult Lung Cancer Occluding a Pulmonary Vein with Suspected Venous Infarction, Mimicking Pneumonia and a Pulmonary Embolus

BackgroundPatients with lung cancer present to the emergency department (ED) in a variety of ways. Symptoms are often nonspecific and can lead to a delay in diagnosis. Here, a lung cancer mimicked two illnesses, adding to the diagnostic complexity. This case highlights diagnostic pitfalls as well as advantages and limitations of imaging utilized in the emergency setting. Case ReportWe report a case of an occult lung cancer occluding a pulmonary vein, which at first mimicked pneumonia and later a pulmonary embolism (PE) and arterial lung infarction. The patient presented to the ED with cough and a lung opacity on chest radiograph that was treated with antibiotics. However, recurrent visits to the ED with similar complaints were further investigated with computed tomography angiogram (CTA). At first the scan was considered positive for PE. Further inspection revealed that the CTA findings were not typical for PE, but rather a slow flow state likely caused by an occult mass occluding a pulmonary vein with venous infarction. Biopsy revealed a lung adenocarcinoma. In addition to the case presentation, the typical signs of PE on CTA with correlating images and diagnostic pitfalls are discussed. Why Should an Emergency Physician Be Aware of This?This case report raises two themes that can be of interest to emergency physicians. The first is that lung cancer has many guises. Here it mimicked two distinctly different diseases, pneumonia and PE. The second is that, although CTA is highly sensitive and specific for diagnosing PE, it has limitations that may lead to false positive readings. When clinical signs and symptoms fail to correlate with the imaging diagnosis, alternative explanations should be sought.

Diagnosis and Treatment of Intracranial Aneurysms with 320-Detector Row Volumetric Computed Tomography Angiography

The objective of the study was to determine the clinical utility of 320-detector row volume-computed tomographic angiography (VCTA) in the management of intracranial aneurysms. Between February 2011 and May 2015, 550 patients successfully underwent 320-detector row VCTA for suspected intracranial aneurysms. Three-dimensional (3D) digital subtraction angiography (DSA) was used as the ultimate reference standard, and the sensitivity, specificity, and accuracy of both nonsubtracted and subtracted VCTA in identifying aneurysms were analyzed. Nonsubtracted VCTA identified 417 aneurysms (2 false-positive readings, 12 false-negative readings). The diagnostic sensitivity, specificity, and accuracy of non-subtracted VCTA, on a per-aneurysm basis, were 97.2%, 99.0%, and 97.6%, respectively. Subtracted VCTA identified 426 aneurysms (2 false-positive readings, 3 false-negative readings). The sensitivity, specificity, and accuracy of subtracted VCTA, on a per-aneurysm basis, were 99.3%, 99.0%, and 99.2%, respectively. No differences in diagnostic accuracy were found between subtracted VCTA and 3D DSA. Nonsubtracted VCTA, however, was observed to be significantly less sensitive than 3D DSA and subtracted VCTA. Twenty-six aneurysm cases were referred for surgical treatment based on VCTA imaging. All aneurysms were deemed completely occluded during surgical clipping. On the basis of VCTA imaging, 299 aneurysms were found suitable for endovascular coiling, of which 293 aneurysms (98%) were treated successfully. The 320-detector row subtracted VCTA technique is an effective, first-line diagnostic imaging modality for surgical and endovascular treatment of aneurysms. The nonsubtracted VCTA was less accurate than the subtracted VCTA, especially for intracranial aneurysms adjoining bone tissue.

Isolated HBsAg positivity in a Mexican patient with newly diagnosed lupus nephritis

IntroductionHepatitis B surface antigen (HBsAg) is usually regarded as a marker of hepatitis B virus (HBV) infection. The concurrence of lupus nephritis (LN) and HBsAg-positivity is a challenge for the clinician, since immunosuppressant use may be associated with an increase in viral replication and an exacerbation of liver disease. Case presentationHere, we describe the case of a 30-year-old Mexican woman with newly diagnosed focal proliferative LN who also tested repeatedly positive for HBsAg by chemiluminescent microparticle immunoassay (CMIA). She had no clinical features of hepatitis and her liver function tests were within normal limits. Her abdominal ultrasound was also normal. While waiting for further results, she was started on lamivudine (100mg daily). However, total HBV core antibody test was negative. Owing to the infrequency of this serological pattern, an in vitro polymerase chain reaction (PCR) assay was performed and HBV was not detected. Overall, we interpreted these results as a false-positive screening. Methylprednisolone pulse therapy was subsequently given (1g daily for three doses) without hepatic repercussion, neither clinically nor biochemically. ConclusionsIsolated HBsAg positivity may result from multiple causes, one of which is cross-reactivity. To the best of our knowledge, this is the first report of a false-positive reading using CMIA technique in an active lupus patient. It is reasonable to stress that lupus patients with a positive screening for HBV should undergo a confirmatory assay (such as genomic detection), since this diagnosis may have important therapeutic implications.

The Role of Laboratory Supervision in Improving the Quality of Malaria Diagnosis: A Pilot Study in Huambo, Angola.

In 2006, the Angolan National Malaria Control Program introduced clinical guidelines for malaria case management, which included diagnostic confirmation of malaria before administration of treatment; however, diagnostic practices were inconsistent and of unknown quality. In 2009, a laboratory supervision program was implemented in Huambo Province, with the goal of assessing and improving diagnosis of malaria within the confines of available in-country resources. Supervisions were carried out from 2009 to 2014 using a standardized supervision tool by national laboratory trainers. Data from the first supervision were compared with that from the final supervision. Over the study period, the number and level of training of laboratory technicians increased, and there was a nonstatistically significant trend toward improved laboratory conditions. There was a significant reduction in false-positive microscopy slide reading (P = 0.0133). Laboratory infrastructural capacity to diagnose other communicable diseases, including syphilis, human immunodeficiency virus and hepatitis B virus infections (P = 0.0012, 0.0233 and 0.0026, respectively), also improved significantly. Laboratory supervision for malaria diagnosis found significant areas for improvement, and in combination with concurrent capacity-building activities, it improved the diagnostic capacity for malaria and other diseases. Importantly, this study demonstrates that locally available resources can be used to improve the accuracy of malaria diagnosis.

Detection of Atrial Fibrillation After Surgical Ablation: Conventional Versus Continuous Monitoring

Current guidelines recommend at least 24-hour Holter monitoring at 6-month intervals to evaluate the recurrence of atrial fibrillation (AF) after surgical ablation. In this prospective multicenter study, conventional intermittent methods of AF monitoring were compared with continuous monitoring using an implantable loop recorder (ILR). From August 2011 to January 2014, 47 patients receiving surgical treatment for AF at 2 institutions had an ILR placed at the time of operation. Each atrial tachyarrhythmia (ATA) of 2 minutes or more was saved. Patients transmitted ILR recordings bimonthly or after any symptomatic event. Up to 27 minutes of data was stored before files were overwritten. Patients also underwent electrocardiography (ECG) and 24-hour Holter monitoring at 3, 6, and 12 months. ILR compliance was defined as any transmission between 0 and 3 months, 3 and 6 months, or 6 and 12 months. Freedom from ATAs was calculated and compared. ILR compliance at 12 months was 93% compared with ECG and Holter monitoring compliance of 85% and 76%, respectively. ILR devices reported a total of 20,878 ATAs. Of these, 11% of episodes were available for review and 46% were confirmed as AF. Freedom from ATAs was no different between continuous and intermittent monitoring at 1 year. Symptomatic events accounted for 187 episodes; however, only 10% were confirmed as AF. ILR was equivalent at detecting ATAs when compared with Holter monitoring or ECG. However, the high rate of false-positive readings and the limited number of events available for review present barriers to broad implementation of this form of monitoring. Very few symptomatic events were AF on review.

Comparison of 3.0-T MR vs 3.0-T MR arthrography of the hip for detection of acetabular labral tears and chondral defects in the same patient population.

We report our experience in diagnostic sensitivity of 3.0-T conventional MR vs 3.0-T MR arthrography of the hip for detection of acetabular labral tears and chondral defects in the same patient population. 43 consecutive patients had both conventional hip MR and MR arthrography examinations performed. These examinations were reviewed retrospectively by independent reading of two musculoskeletal radiologists who read the MR and MR arthrogram examinations in a randomized fashion (i.e. MR and MR arthrogram examinations were read at separate sittings and in a randomized fashion so as not to bias reviewers). Scans were assessed for acetabular labral tears and chondral defects. All patients went on to arthroscopy. Of these 43 patients, 40 had acetabular labral tears read by Reader 1 and 39 had acetabular labral tears read by Reader 2 on MR arthrogram, 39 had acetabular labral tears read by Reader 1 and 38 had acetabular labral tears read by Reader 2 on conventional MR examination. There were 42 labral tears in 43 patients at arthroscopy. There were four false-negative labral tears compared with arthroscopy on MR and three false negatives on MR arthrography for Reader 1 and five false negatives on MR and four false negatives on MR arthrography for Reader 2. Each reader had one false-positive labral tear compared with arthroscopy on both MR and MR arthrography. There were 32 acetabular chondral defects at arthroscopy. Reader 1 saw 21 acetabular chondral defects on conventional MR and 27 chondral defects at MR arthrography. Reader 2 saw 19 acetabular chondral defects at conventional MR and 25 acetabular chondral defects on MR arthrography. There were no false-positive readings of chondral defects compared with arthroscopy on MR and one false positive for Reader 1 and two false positives for Reader 2 on MR arthrography as compared with arthroscopy. On conventional MR examination, sensitivities and specificities as compared with arthroscopy were as follows: Reader 1 acetabular labral tear (90% sensitivity, 0% specificity) and Reader 2 acetabular labral tear (88% sensitivity, 0% sensitivity). On MR arthrogram, sensitivities and specificities as compared with arthroscopy for Reader 1 were 93%, 0% and for Reader 2 were 90%, 0%, respectively. Sensitivities and specificities for detection of acetabular chondral defects as compared with arthroscopy were Reader 1 conventional MR (65% sensitivity, 100% specificity), Reader 1 MR arthrography (81% sensitivity, 91% specificity), Reader 2 conventional MR (59% sensitivity, 100% specificity) and Reader 2 MR arthrography (71% sensitivity, 82% specificity). In this series, 3.0-T MR demonstrated sensitivity for detection of acetabular labral tears that rivals the sensitivity of 3.0-T MR arthrography of the hip. In this series, 3.0-T MR arthrography was more sensitive than conventional 3.0-T MR for detection of acetabular chondral defects. 3.0-T MR and MR arthrography are near equivalent in the diagnosis of acetabular labral tears. This information is useful for pre-operative planning.

Abstract T MP107: Measurement of Acute Brain Hemorrhage in the Pre-hospital Setting

Purpose: Delay in identification and treatment of hemorrhagic stroke can result in severe disability and death. Differentiation of acute stroke is essential to successful emergency treatment and patient outcome. A head CT scan is the gold standard for identifying hemorrhagic stroke. This pilot study evaluates utilization of a handheld infra-red screening device for possible detection of hemorrhagic stroke in the pre-hospital setting. Methods: The study involved collaboration with regional emergency medical services. Device education and competencies were completed by all paramedics. A stroke assessment form was utilized in conjunction with the device on all patients experiencing signs and symptoms of acute stroke. Data obtained by the device was compared to the initial head CT scan obtained in the hospital Emergency Trauma Center. Results: A total of 46 patients were enrolled in this pilot study. The device and head CT data were evaluated on ability to detect the presence of hemorrhagic stroke. Of the 46 patients, 7 patients were admitted with hemorrhagic stroke after positive head CT results. Out of these 7 patients, 5 had positive device results. There were 14 patients admitted with a diagnosis of acute ischemic stroke, 8 of these patients had false positive device results. Stroke mimic enrollment included 25 patients, 15 with false positive device results. Conclusion: The handheld infra-red screening device detected all hemorrhagic stroke cases that were within the detection abilities of the system. Large vessel ischemic strokes scanned by EMS demonstrated increased blood flow and on the opposite side of the ischemic lesion. Stroke mimics included cardiac abnormality, seizure and dehydration. Several challenges in the use of the device are noted. The 2-3 minutes it took EMS to scan correctly, was too long for scanning stroke patients, decreasing this measurement time appeared to contribute to false positive results. Measurements performed during fast ambulance transport appeared to also cause false positive readings. Difficulty to achieve reliable measurement was also noted with combative and epileptic patients. EMS feedback was provided to the device manufacturer. The researchers recommend continued research to support this effort.

Evolution of the MIDTAL microarray: the adaption and testing of oligonucleotide 18S and 28S rDNA probes and evaluation of subsequent microarray generations with Prymnesium spp. cultures and field samples.

The toxic microalgal species Prymnesium parvum and Prymnesium polylepis are responsible for numerous fish kills causing economic stress on the aquaculture industry and, through the consumption of contaminated shellfish, can potentially impact on human health. Monitoring of toxic phytoplankton is traditionally carried out by light microscopy. However, molecular methods of identification and quantification are becoming more common place. This study documents the optimisation of the novel Microarrays for the Detection of Toxic Algae (MIDTAL) microarray from its initial stages to the final commercial version now available from Microbia Environnement (France). Existing oligonucleotide probes used in whole-cell fluorescent in situ hybridisation (FISH) for Prymnesium species from higher group probes to species-level probes were adapted and tested on the first-generation microarray. The combination and interaction of numerous other probes specific for a whole range of phytoplankton taxa also spotted on the chip surface caused high cross reactivity, resulting in false-positive results on the microarray. The probe sequences were extended for the subsequent second-generation microarray, and further adaptations of the hybridisation protocol and incubation temperatures significantly reduced false-positive readings from the first to the second-generation chip, thereby increasing the specificity of the MIDTAL microarray. Additional refinement of the subsequent third-generation microarray protocols with the addition of a poly-T amino linker to the 5' end of each probe further enhanced the microarray performance but also highlighted the importance of optimising RNA labelling efficiency when testing with natural seawater samples from Killary Harbour, Ireland.

Comparing Standing Heat and Estrotect Heat Detection Patches

A recent survey showed that 66% of producers surveyed used some amount of heat detection in their artificial insemination program, and 74% of producers that used heat detection aids had tried Estrotect (Rockway, Inc.; Spring Valley, WS) heat detection patches. The peel-and-stick application made Estrotect more popular than types that required adhesive application. The patches are designed so that when the animal is mounted the top surface layer is removed, much like scratching a lottery ticket. After several mounts the entire layer is removed, leaving a bright-colored surface behind. A new type of patch, Standing Heat (Standing Heat, LLC; Dannebrog, NE), was recently released and has a surface layer designed to rub off with the goal of reducing false positive readings due to inadvertent scratches such as from branches or tail switching. The objective of the current study was to compare the efficacy of two different heat detection patches.

Determining fever in children: the search for an ideal thermometer

Body temperature measurement is most commonly taken to confirm the presence or absence of fever. Many decisions concerning the investigation and treatment of children are based on the results of temperature measurement alone. Determining the presence of fever in young children is particularly important. A missed fever is serious, but a false-positive fever reading can result in unnecessary septic workups. The axillary, rectal, oral and tympanic membrane sites are most commonly used to record body temperature, and electronic and infrared thermometers are the devices most commonly used. Each site and device has numerous advantages and disadvantages, which are described in this article. The search for the means of measuring body temperature that best combines accuracy, speed, convenience, safety and cost-effectiveness goes on. The infrared thermometer and the tympanic site appear to offer such a combination. Electronic thermometers are also suitable when used orally or at the axilla in newborn babies.

Real-Time Breath-to-Breath Asynchrony Event Detection using Time-Varying Respiratory Elastance Model

Asynchronous events (AE) occur during mechanical ventilation (MV) therapy when the patient's breathing is not synchronised with the ventilator support. Frequent AE indicates sub-optimal ventilation therapy and may lead to further complications. Asynchrony Index (AI) gives the percentage of AEs as a percentage of total breaths, but is only assessed via manual scrutiny. Thus, there is a need to automate AE detection in real-time. A model-based approach using time-varying elastance to detect AEs is developed and retrospectively assessed in MV patients. Data from 14 mechanically ventilated respiratory failure patients, enrolled in an observational study in Christchurch Hospital, New Zealand were used to investigate the performance of the method. Patient data is sorted according to the ventilation mode used, and AI is calculated for each episode separately. The model-based approach accurately identifies AEs, and shown not to give false positive readings when compared to manual detection (gold standard). None of the ventilation modes give significantly different AI levels (P > 0.05). AI decreases when ventilation mode changes and increases overall time indicate worsen patient-ventilator interaction. The model-based method is able to successfully and accurately calculate AI. Real time use of this metric will enable patients with sub-optimal ventilator settings to be automatically identified for the first time and the settings adjusted as necessary, improving the efficacy of mechanical ventilation therapy, and providing a quantified metric to help guide MV care.

Addressing False Positives in Early Reading Assessment Using Intervention Response Data

The current study examined a solution to high false positive reading risk classification rates in early kindergarten by investigating a method of identifying students with possible false positive risk classifications and returning them to general classroom instruction. Researchers assessed kindergarten students ( N = 105) identified as at risk who were participating in a full-year Tier 2 reading intervention program. Students with very strong initial curriculum mastery ( n = 9) were identified as having possible false positive risk classifications and returned to general classroom Tier 1 instruction. Very strong responders who were exited from intervention (i.e., exited strong responders) scored above the risk range across multiple reading measures at the end of the year and performed similarly to a historical comparison cohort who remained in intervention services for the entire year (i.e., treated strong responders). Results suggest that kindergarten students with false positive risk classifications can be identified after a period of intervention services and successfully returned to general classroom instruction.

False positives in Biolog EcoPlatesTM and MT2 MicroPlatesTM caused by calcium

Biolog MicroPlatesTM (e.g. EcoPlateTM, MT2 MicroPlateTM, GN MicroPlateTM) are useful tools for characterizing microbial communities, providing community-level physiological profiles to terrestrial and aquatic ecologists. The more recently designed Biolog EcoPlates have been used frequently in aquatic ecology with success. This study, however, reveals one major problem when using EcoPlates to evaluate samples within an estuarine or seawater matrix. At concentrations greater than 100 parts per million, the cation calcium begins to interfere with the microplate chemistry, causing false positive readings. Experiments, in which multiple treatments of natural and artificial seawater were tested, as well as calcium-addition experiments, demonstrate that calcium inhibits complete dissolution of the minimal growth medium in wells. Future studies involving Biolog EcoPlates and MicroPlates should take this effect into account, and the dilution of samples is strongly recommended to diminish the “calcium effect.”

Impact of Body Mass Index on the Detection of Radiographic Localized Pleural Thickening

Subpleural fat can be difficult to distinguish from localized pleural thickening (LPT), a marker of asbestos exposure, on chest radiographs. The aims of this study were to examine the influence of body mass index (BMI) on the performance of radiograph readers when classifying LPT and to model the risk of false test results with varying BMI. Subjects (n=200) were patients being screened or treated for asbestos-related health outcomes. A film chest radiograph, a digital chest radiograph, and a high-resolution computed tomography (HRCT) chest scan were collected from each subject. All radiographs were independently read by sevenB readers and scored using the International Labour Office system. HRCT scans, read by three experienced thoracic radiologists, served as the gold standard for the presence of LPT. We calculated measures of radiograph reader performance, including sensitivity and specificity, for each image modality. We also used logistic regression to estimate the probability of a false-positive and a false-negative result while controlling for covariates. The proportion of false-positive readings correlated with BMI. While controlling for covariates, regression modeling showed the probability of a false-positive result increased with increasing BMI category, younger age, not having pleural calcification, and among subjects not reporting occupational or household contact asbestos exposure. Clinicians should be cautious when evaluating radiographs of younger obese persons for the presence of asbestos-related pleural plaque, particularly in populations having an anticipated low or background prevalence of LPT.

Analysis of the germination kinetics of individual Bacillus subtilis spores treated with hydrogen peroxide or sodium hypochlorite

More than 95% of individuals in populations of Bacillus subtilis spores killed approximately 95% by hydrogen peroxide or hypochlorite germinated with a nutrient, although the germination of the treated spores was slower than that of untreated spores. The slow germination of individual oxidizing agent-treated spores was due to: (i) 3- to 5-fold longer lag times (Tlag ) between germinant addition and initiation of fast release of spores' large dipicolinic acid (DPA) depot (ii) 2- to 10-fold longer times (ΔTrelease ) for rapid DPA release, once this process had been initiated; and (iii) 3- to 7-fold longer times needed for lysis of spores' peptidoglycan cortex. These results indicate that effects of oxidizing agent treatment on subsequent spore germination are on: (i) nutrient germinant receptors in spores' inner membrane (ii) components of the DPA release process, possibly SpoVA proteins also in spores' inner membrane, or the cortex-lytic enzyme CwlJ; and (iii) the cortex-lytic enzyme SleB, also largely in spores' inner membrane. This study further indicates that rapid assays of spore viability based on measurement of DPA release in spore germination can give false-positive readings. This work shows that with Bacillus subtilis spore populations in which approximately 95% of individual spores were killed by several oxidizing agents, >95% of the spores in these populations germinated with nutrients, albeit slowly. This is important, as assay of an early germination event, release of dipicolinic acid, has been suggested as a rapid assay for spore viability and would give false-positive readings for the level of the killing of oxidizing agent-treated spore populations. Analysis of the germination kinetics of multiple individual untreated or oxidizing agent-treated spores also provides new information on proteins damaged by oxidizing agent treatment, and at least some of which are in spores' inner membrane.

Cognitive and System Factors Contributing to Diagnostic Errors in Radiology

In this article, we describe some of the cognitive and system-based sources of detection and interpretation errors in diagnostic radiology and discuss potential approaches to help reduce misdiagnoses. Every radiologist worries about missing a diagnosis or giving a false-positive reading. The retrospective error rate among radiologic examinations is approximately 30%, with real-time errors in daily radiology practice averaging 3-5%. Nearly 75% of all medical malpractice claims against radiologists are related to diagnostic errors. As medical reimbursement trends downward, radiologists attempt to compensate by undertaking additional responsibilities to increase productivity. The increased workload, rising quality expectations, cognitive biases, and poor system factors all contribute to diagnostic errors in radiology. Diagnostic errors are underrecognized and underappreciated in radiology practice. This is due to the inability to obtain reliable national estimates of the impact, the difficulty in evaluating effectiveness of potential interventions, and the poor response to systemwide solutions. Most of our clinical work is executed through type 1 processes to minimize cost, anxiety, and delay; however, type 1 processes are also vulnerable to errors. Instead of trying to completely eliminate cognitive shortcuts that serve us well most of the time, becoming aware of common biases and using metacognitive strategies to mitigate the effects have the potential to create sustainable improvement in diagnostic errors.

Characterization of a parietal lesion detected by diffusion weighted MRI, NaF18-PET/CT and CT

It is very important to accurately characterize skull lesions so that appropriate treatment decisions can be made. False positive readings may lead to unnecessary surgical intervention or radiation. We present a case of a parietal lesion seen on Diffusion weighted (DW) MRI, and further characterized with NaF18-PET/CT and CT in a 69 year old male. This is the first case to report the use of DW MRI, NaF18-PET/CT bone scan and CT in the diagnosis of a skull lesion. DW MRI is known to have high specificity to detect malignant lesions in the skull. If a similar case such as ours in encountered in everyday clinical practice, a differential diagnosis of a benign etiology should be considered.

Potential of Chlorophyll-Rich Feed Ingredients To Improve Detection of Fecal Contamination in the Abattoir

The use of fecal fluorescence to improve detection of contamination of carcasses in the abattoir was previously reported. However, incidents of false negatives can result when animals are offered diets that contain little chlorophyll (e.g., concentrate). Here, we investigated the potential of incorporating a high-chlorophyll-containing feed ingredient (concentrated alfalfa extract; CAE) into the diets of sheep and cattle to improve fecal fluorescence intensity. The sheep experiment evaluated the fecal fluorescence of animals from pasture, when fed a concentrate-barley straw diet and when the concentrate diet incorporated CAE (100 g of dry matter a day). Fecal chlorophyll and metabolite content was highest on the pasture-fed animals and increased significantly over the concentrate diet when CAE was included. Subsequently fluorescent intensity was increased from 15,000 to 36,000 arbitrary units for concentrate and CAE-concentrate diets, respectively, compared with 59,000 for the pasture-fed animals. The cattle experiment investigated the potential of CAE to improve fluorescence of feces from a concentrate diet as well as a silage diet at two levels of incorporation (75 and 150 g CAE/kg of dry matter intake). This study also determined the fluorescence of digesta and carcass contamination in the abattoir on a subset of carcasses. In agreement with the sheep study, CAE significantly improved fluorescence of feces and digesta when added to a concentrate diet, but had little effect on improving fecal fluorescence from the silage-fed animals. This was thought to be related to greater chlorophyll degradation in the rumen or/and the dark nature of the silage feces acting as a quencher of emitted fluoresced light. Incorporating high-chlorophyll-containing plant ingredients into ruminant concentrate diets will improve detection of fecal contamination by reducing false-negative readings. However, they will have little effect on false-positive readings due to the range of wavelengths emitted by natural chlorophyll and its metabolites. Implications and potential solutions for this are discussed.

Laboratory and field testing of a remotely deployed, multi-sensor fluorometer for groundwater tracing in an Ozark environment

In fall of 2008, the Missouri Geological Survey Program, Missouri Department of Natural Resources began testing a remotely deployed, multi-sensor submersible fluorometer. The submersible data logging fluorometer is capable of integrating up to six sensors, including fluorescence and turbidity, with the device’s standard temperature and pressure sensors. Fluorescein, Rhodamine WT™ (Acid Red 388, manufactured by Chemcentral), optical brightener, and turbidity probes were installed on the unit. The instrument measures fluorescence in relative fluorescence units (RFU) that can be correlated to known concentrations. Data from laboratory testing indicated that the unit was capable of detecting tested water tracers in concentrations as low as one part per billion (ppb) in a zero turbidity environment and at concentrations of 10 ppb, even in turbid water. Background reflectance and fluorescence levels from organics in the environment and other tracers were determined to be insignificant for the fluorescein and optical brightener sensors. However, the Rhodamine WT probe gave false-positive readings when fluorescein dye was present due to spectral overlap from the fluorescein sensors excitations source. Spectral overlap was reduced to <1 % at all concentrations with the addition of a light-reducing shield to the Rhodamine WT sensor. The unit allowed simultaneous detection of multiple fluorescent water tracers and measured water quality parameters during extended remote deployments for continuous field monitoring. Field testing indicated the fluorometer was reliable detecting the three tracers tested and more precisely delineating the time of travel for tracers than conventional methods. Field testing revealed the unit provides more confidence in the detection of optical brightener than using carbon packet sampling methods and was less time consuming that collecting and analyzing numerous water samples.

Common Hand Sanitizer May Distort Readings of Breathalyzer Tests in the Absence of Acute Intoxication

The use of alcohol-based hand sanitizers has recently become widespread. To the authors' knowledge, no previous study has examined whether application of ethanol-based hand sanitizers by the person operating a common breathalyzer machine will affect the accuracy of the readings. This was a prospective study investigating whether the use of hand sanitizer applied according to manufacturer's recommendations (Group I), applied improperly at standard doses (Group II), or applied improperly at high doses (Group III) had an effect on breathalyzer readings of individuals who had not ingested alcohol. The participants of the prospective study were divided into three groups to assess the effect of hand sanitizer on breathalyzer readings. Group I used one pump (1.5 mL) of hand sanitizer (Purell), allowing the hands to dry per manufacturer's recommendations; Group II used one pump (1.5 mL), without allowing the hands to dry; and Group III used two pumps (3 mL), without allowing the hands to dry. Breathalyzer measures for each group are presented as medians with interquartile ranges (IQR) and ranges. Differences between each sequential group (I vs. II and II vs. III) were assessed using a Mann-Whitney U-test (p < 0.05 significant). There were 25 study participants in each group for a total of 75 participants. The initial breathalyzer readings of all study participants were 0.000 g/dL. The median breathalyzer reading was 0.004 g/dL in Group I (IQR = 0.001 to 0.008 g/dL), 0.051 g/dL in Group II (IQR = 0.043 to 0.064 g/dL), and 0.119 g/dL in Group III (IQR = 0.089 to 0.134 g/dL). Measures between each subsequent group were all statistically different (p < 0.001). The use of common alcohol-based hand sanitizer may cause false-positive readings with a standard hospital breathalyzer when the operator uses the hand sanitizer correctly. The breathalyzer readings are further elevated if more sanitizer is used or if it is not allowed to dry appropriately.