Biomedical subjects

D J Karras

Publications and source records attributed to D J Karras.

9 recordsLinked to original sources

PubMed1998

Absolute lymphocyte count as a predictor of CD4 count.

STUDY OBJECTIVE: To determine whether the absolute lymphocyte count (ALC) (white blood count x lymphocyte percentage) can be used to predict a low CD4 count. METHODS: We conducted a retrospective data analysis of consecutive CD4 count analyses performed between January 1, 1995, through December 1, 1995, at an urban university teaching hospital. Results of consecutive CD4 counts and simultaneously measured ALCs were analyzed from samples obtained in inpatient, clinic, and emergency department settings. The ability of ALC to predict a CD4 count less than 200 cells/mm3 was analyzed by calculating sensitivities, specificities, predictive values, and likelihood ratios for a range of ALC values. RESULTS: Among the 807 samples, 322 results (40%) had a CD4 count less than 200 cells/mm3. The ALC and CD4 count were correlated (r=.69, P<.0001). An ALC less than 1,000 cells/mm3 predicted CD4 counts less than 200 cells/mm3 with a sensitivity of .67 (95% confidence interval .62 to .72), specificity of .96 (.94 to .98), positive predictive value of .91 (.87 to .95), and a negative predictive value of .81 (.78 to .84). An ALC less than 2,000 cells/mm3 predicted CD4 counts less than 200 cells/mm3 with a sensitivity of .97 (.95 to .99), specificity of .41 (.37 to .45), positive predictive value of .52 (.48 to .56), and negative predictive value of .95 (.92 to .98). CONCLUSION: A reliable relationship exists between ALC and CD4 count. In a similar population, an ALC less than 1,000 cells/mm3 is predictive of a CD4 count less than 200 cells/mm3, and an ALC greater than or equal to 2,000 cells/mm3 is predictive of a CD4 count greater than or equal to 200 cells/mm3. Physicians may find these criteria useful in identifying patients with increased risk of opportunistic infection.

AIDS-Related Opportunistic Infections↗

PubMed1998

Tick removal.

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Animals↗

PubMed1997

Statistical methodology: II. Reliability and variability assessment in study design, Part A.

Assessment of test reliability and validity is often complex. Although tests of correlation are frequently used to measure interest agreement, such indexes measure only the strength of the linear relationship between variables and may not provide an accurate assessment of the correspondence between test results. Inspection of interest differences, either visually or using the r1, may provide a better indicator of the correspondence between test results and accounts for measurement biases. Strength of association between categorical variables can be measured using related tests such as the kappa statistic. Test reliability may be assessed by retesting, but this is not practical in many cases when subject memory or learning may confound the results of repeated examinations. Several methods exist for determining reliability from a single test administration and for assessing the correspondence between answers to homogeneous test questions. In the continuation article (Part B) on this subject, the concept and assessment of validity will be examined in more detail, and techniques for maximizing the reliability and validity of questionnaires will be discussed.

Emergency Medicine↗

PubMed1997

Statistical methodology: II. Reliability and validity assessment in study design, Part B.

Validity measures the correspondence between a test and other purported measures of the same or similar qualities. When a reference standard exists, a criterion-based validity coefficient can be calculated. If no such standard is available, the concepts of content and construct validity may be used, but quantitative analysis may not be possible. The Pearson and Spearman tests of correlation are often used to assess the correspondence between tests, but do not account for measurement biases and may yield misleading results. Techniques that measure interest differences may be more meaningful in validity assessment, and the kappa statistic is useful for analyzing categorical variables. Questionnaires often can be designed to allow quantitative assessment of reliability and validity, although this may be difficult. Inclusion of homogeneous questions is necessary to assess reliability. Analysis is enhanced by using Likert scales or similar techniques that yield ordinal data. Validity assessment of questionnaires requires careful definition of the scope of the test and comparison with previously validated tools.

Humans↗

PubMed1996

Poisoning from "Spanish fly" (cantharidin).

Cantharidin, known popularly as Spanish fly, has been used for millennia as a sexual stimulant. The chemical is derived from blister beetles and is notable for its vesicant properties. While most commonly available preparations of Spanish fly contain cantharidin in negligible amounts, if at all, the chemical is available illicitly in concentrations capable of causing severe toxicity. Symptoms of cantharidin poisoning include burning of the mouth, dysphagia, nausea, hematemesis, gross hematuria, and dysuria. Mucosal erosion and hemorrhage is seen in the upper gastrointestinal (GI) tract. Renal dysfunction is common and related to acute tubular necrosis and glomerular destruction. Priapism, seizures, and cardiac abnormalities are less commonly seen. We report four cases of cantharidin poisoning presenting to our emergency department with complaints of dysuria and dark urine. Three patients had abdominal pain, one had flank pain, and the one woman had vaginal bleeding. Three had hematuria and two had occult rectal bleeding. Low-grade disseminated intravascular coagulation, not previously associated with cantharidin poisoning, was noted in two patients. Management of cantharidin poisoning is supportive. Given the widespread availability of Spanish fly, its reputation as an aphrodisiac, and the fact that ingestion is frequently unwitting, cantharidin poisoning may be a more common cause of morbidity than is generally recognized. Cantharidin poisoning should be suspected in any patient presenting with unexplained hematuria or with GI hemorrhage associated with diffuse injury of the upper GI tract.

Adolescent↗

PubMed1995

Is circadian variation in asthma severity relevant in the emergency department?

STUDY OBJECTIVE: Asthmatic patients have marked circadian variation in disease severity, with bronchospasm far worse between midnight and 8 AM than at other times of day. In this study we sought to determine whether circadian variation in asthma severity is clinically relevant for purposes of emergency management. DESIGN: Prospective, observational cohort study. SETTING: The emergency department of a large urban university hospital. PARTICIPANTS: Asthmatic patients 16 years and older who presented with the complaint of asthma exacerbation. RESULTS: Peak expiratory flow rate (PEFR), respiratory rate, and objective and subjective assessments of dyspnea severity were determined at the time of each patient's presentation to the ED and at the time of disposition decision. Time of symptom onset, duration of symptoms, response to therapy, and final disposition were recorded. Nocturnal presentation and onset were defined as arrival in the ED or onset of symptoms between midnight and 8 AM. We enrolled 188 asthmatic patients in the study; 52 (28%) presented nocturnally. Comparison of asthmatic patients who presented nocturnally and those who presented at other times revealed no differences in initial or final PEFR or respiratory rate, change in PEFR, subjective or objective dyspnea, or rate of hospitalization, although nocturnal patients did have a significantly shorter ED treatment time. Analysis by time of symptom onset also revealed no differences between nocturnally and nonnocturnally presenting subjects in disease severity or outcome, with the exception that those with nocturnal symptom onset had less subjective dyspnea than other asthmatic patients. Repeat analysis with different "nocturnal" time periods did not alter the results. CONCLUSION: In our study group, asthmatic patients who presented nocturnally to the ED did not differ from other asthmatic patients in disease severity and therefore do not appear to represent a unique population for purposes of ED management or disposition decisions.

Adolescent↗

PubMed1995

Chest pain associated with cocaine: an assessment of prevalence in suburban and urban emergency departments.

STUDY OBJECTIVE: Chest pain and myocardial infarction following the use of cocaine have been well documented. We assessed the prevalence of cocaine use in patients who presented to the emergency department with chest pain of possibly ischemic origin. DESIGN: During times of research assistant availability, consecutive adults with the chief complaint of chest pain unexplained by trauma or radiographic abnormality were questioned about cocaine use in the preceding week. Urine was tested for the presence of cocaine or cocaine metabolites with a highly accurate bedside urine test kit (specificity, 100%; sensitivity 98%). Anonymous unlinked data-collection methods were used. Therefore we could not determine whether the patients who used cocaine had sustained myocardial infarctions. SETTING: One suburban and three urban EDs. RESULTS: We enrolled 359 patients with a mean age of 51 years, 8% of whom sustained myocardial infarctions. Sixty patients (17%) had cocaine or cocaine metabolites in urine. The likelihood of testing positive for cocaine varied by age group: 18 to 30 years, 29%; 31 to 40 years, 48%; 41 to 50 years, 18%; 51 to 60 years, 3%; 61 years or older, 0% (P < .0001). Of the 60 patients who tested positive for cocaine, only 43 (72%) admitted recent use. CONCLUSION: Many ED patients with chest pain have recently used cocaine. Because the recent use of cocaine is not uncommon in patients with chest pain up to 60 years old, such patients should be questioned about cocaine use. When treatment or disposition may be altered, consideration should be given to objective assessment of cocaine use because patient self-report does not appear reliable.

Adolescent↗

PubMed1995

Comprehension of discharge instructions by patients in an urban emergency department.

STUDY OBJECTIVE: To assess patients' comprehension of their emergency department discharge instructions and to determine if inner-city patients' literacy levels are adequate to comprehend written discharge instructions. DESIGN: Prospective, observational study. SETTING: The ED of an inner-city university hospital. PARTICIPANTS: Two hundred seventeen patients consecutively discharged from the ED during 12 separate time slots. INTERVENTIONS: Patients were interviewed after discharge from the ED and asked to state their diagnosis, medication instructions, and follow-up instructions. Comparisons between patient recall and instructions as written in the chart were assessed by independent raters and scored from poor to excellent. Patients were administered a standardized test of reading ability. RESULTS: Overall comprehension rates were judged to be good, although 23% of patients exhibited no understanding of at least one component of their discharge instructions. Mean reading ability of the patients was at the sixth-grade level. The ED's printed discharge instructions were written at an 11th-grade reading level. Patients with low literacy scores were more likely to have poor comprehension of instructions. CONCLUSION: Overall comprehension rates in this population were good despite the fact that ED instruction sheets were written at an inappropriately high reading level. Verbal instructions given by the discharging physician likely have a significant effect on patients' comprehension of instructions.

Adult↗

PubMed1994

Severe low back pain secondary to acute interstitial nephritis following administration of ranitidine.

Acute interstitial nephritis is a disease characterized by renal inflammation and is thought to be secondary to a hypersensitivity reaction. Although the causes of acute interstitial nephritis are numerous, adverse reactions to many common drugs, particularly antibiotics and nonsteroidal anti-inflammatory agents, are important etiological factors. Acute interstitial nephritis has many clinical manifestations, most notably fever and rash. Flank pain is an uncommon presentation. A case of acute, severe, low-back pain and rash in a healthy woman found to be secondary to acute interstitial nephritis is reported. The etiology of acute interstitial nephritis in this patient's case is suspected to be ranitidine (Zantac; Glaxo Pharmaceuticals, Research Triangle Park, NC), which has not been previously associated with this syndrome.

Acute Disease↗