The Vitals - March 2016
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Physicians in South Florida, Texas Most Likely to See Zika Outbreak
BOULDER, CO – How likely you are to see a Zika virus outbreak this summer varies greatly based on where you practice.
A new study led by mosquito and disease experts at the National Center for Atmospheric Research (NCAR) reports that populations of the Aedes aegypti mosquito, responsible for the spread of the virus in much of Latin America and the Caribbean, are likely to increase across much of the southern and eastern United States as the weather warms up.
The research, published recently in PLOS Currents Outbreaks, notes that summertime weather conditions are favorable for populations of the mosquito along the East Coast as far north as New York City and across the southern tier of the country as far west as Phoenix and Los Angeles. Those predictions are based on specialized computer simulations conceived and run by researchers at NCAR and the NASA Marshall Space Flight Center.
The mosquitoes should subside during spring and fall except for low-to-moderate populations in more southern regions, but winter is too cold for the species outside of the more southern areas of Florida and Texas, according to the simulations.
Most vulnerable overall are cities in southern Florida and areas of southern Texas, much of it poor and rural, according to researchers who determined that by analyzing travel patterns from countries and territories with Zika outbreaks.
"This research can help us anticipate the timing and location of possible Zika virus outbreaks in certain U.S. cities," said lead author Andrew Monaghan, PhD, of NCAR. "While there is much we still don't know about the dynamics of Zika virus transmission, understanding where the Aedes aegypti mosquito can survive in the U.S. and how its abundance fluctuates seasonally may help guide mosquito control efforts and public health preparedness."
Miami, Houston, and Orlando were among the cities with the highest potential numbers of Aedes aegypti as well as a large volume of air travelers. And, because nearly five times as many people cross the U.S.-Mexico border per month than arrive by air in all 50 cities, study authors wrote, that creates a high potential for transmission in border areas from Texas to California, although the Zika virus has not been widely reported in northern Mexico.
"Even if the virus is transmitted here in the continental U.S., a quick response can reduce its impact," added co-author Mary Hayden, PhD, a medical anthropologist also at NCAR.
Long-range forecasts for this summer suggest a 40-45% chance of warmer-than-average temperatures over most of the continental United States, advised study authors who also cautioned that the report doesn’t include a specific outbreak prediction for this year.
Monaghan said warmer weather would increase suitability for Aedes aegypti in much of the South and East, although above-normal temperatures would be less favorable for the species in the hottest regions of Texas, Arizona, and California.
Even if Zika cases become more common in the United States, the disease is unlikely to spread as widely as it has in Latin America and the Caribbean, partly because Americans spend so much time in air-conditioned and largely sealed homes and offices.
Zika, first identified in Uganda in 1947, has moved through tropical regions of the world over the past decade before being introduced into Brazil last year. It burgeoned across Latin America and the Caribbean, with more than 20 countries now facing pandemics.
Study authors point out that about 80% of infected people do not have significant symptoms, and, even when symptoms appear, they tend to be relatively mild flu- or cold-like and resolve in about a week. The concern is that the disease can lead to microcephaly, a rare birth defect characterized by an abnormally small head and brain damage, when contracted by pregnant women.
The study noted that northern cities could become more vulnerable if a related species of mosquito that is more tolerant of cold temperatures, Aedes albopictus, begins to carry the virus.
Study Finds High Risks of Warfarin Use in Older AF Patients
NEW YORK – For physicians already hesitant to prescribe oral anticoagulants to older adults with atrial fibrillation (AF), here’s some bad news: The risks might be worse than you suspected.
A study in JAMA Cardiology points out that older age is a significant risk factor for thromboembolic stroke in patients with AF, and that drug therapy with warfarin reduces the threat by almost two-thirds in patients at high risk. At the same time, however, traumatic intracranial bleeding, usually caused by a fall, is a great concern.
The study, led by New York University School of Medicine researchers, looked at 31,951 U.S. veterans with AF, 75 years or older, who were new referrals to Veterans Affairs (VA) anticoagulation clinics between 2002 and 2012.
The rate of traumatic intracranial bleeding among older adults with AF initiating warfarin therapy actually was higher than previously reported in clinical trials. Among the factors putting patients at increased risk of traumatic intracranial bleeding were dementia, anemia, depression, anticonvulsant use, and labile international normalized ratio (INR).
With a mean patient age of 81.1 in the almost all-male study group, the incidence rate of hospitalization for traumatic intracranial bleeding was 4.80 per 1000 person-years, according to the results. The incidence rates of hospitalization for any intracranial bleeding and ischemic stroke were 14.58 and 13.44, respectively.
Comorbidities were common, including hypertension (82.5%), coronary artery disease (42.6%), and diabetes mellitus (33.8%).
“Among patients 75 years or older with atrial fibrillation initiating warfarin therapy, the risk factors for traumatic intracranial bleeding are unique from those for ischemic stroke,” the study concluded. “The high overall rate of intracranial bleeding in our sample supports the need to more systematically evaluate the benefits and harms of warfarin therapy in older adults.”
Authors note that they were unable to generate a clinical prevention tool to evaluate risk but “still believe that the individual factors we identified may potentially be used in patient-centered discussions about the benefits and harms of warfarin therapy in older adults.” They also call for validation in other data sets, including more women.
Why Difficult Patients Make Correct Diagnosis Less Likely
ROTTERDAM, THE NETHERLANDS – As much time as you might spend trying to get it right, you’re more likely to get a diagnosis wrong when dealing with “difficult” patients.
That’s according to new Dutch studies published in BMJ Quality & Safety, which find that physicians often are distracted from processing clinical information by problematic behavior.
A study team led by Erasmus Medical Center researchers provided 63 physicians in the last year of their specialty training in family medicine with one of two versions of six clinical case scenarios. While one version featured a “difficult” patient with one of six conditions, another described the same patient with neutral behavior.
Difficult behaviors portrayed included the following:
- a demanding patient,
- an aggressive patient,
- one who questions the doctor's competence,
- one who ignores the doctor's advice,
- one who doesn't expect the doctor to take him seriously, and
- one who is utterly helpless.
The six conditions, meanwhile, were pneumonia, pulmonary embolism, meningoencephalitis, hyperthyroidism, appendicitis, and acute alcoholic pancreatitis.
With the last three cases designated as more complex, all included a brief description of the patient's medical history, their signs and symptoms, and the results of the physical examination.
Participants were asked to write down the most likely diagnosis as quickly as possible. They then were asked to review the same case, writing down the information for and against the diagnosis they had made, and to offer an alternative if they believe they had gotten it wrong the first time around.
At the end, they were asked to rate the likeability of the patient, using a validated (Likert) scale.
Diagnostic accuracy was higher for simpler cases, as expected, but the physicians were also 42% more likely to misdiagnose a difficult patient than a “neutral” one in a complex case, and 6% more likely to do so in a simple case.
Extra time spent on diagnosis didn’t change that, and, while further reflection improved diagnostic accuracy, it still didn't make up for the effect of disruptive behavior. In addition, the average likeability ratings were significantly lower for patients portrayed as '”difficult” than they were for those portrayed as behaving neutrally.
In a second study, researchers found that diagnostic accuracy was 20% lower for difficult patients, this time also including a patient who threatens the doctor and another who accuses the doctor of discrimination, even though the time spent on diagnosis was similar. Participants recalled proportionally fewer clinical findings — 30% vs. 32.5% — and more behavioral issues — 25% vs.18% — in those patients.
“Difficult patients’ behaviors induce doctors to make diagnostic errors, apparently because doctors spend part of their mental resources on dealing with the difficult patients’ behaviors, impeding adequate processing of clinical findings,” study authors concluded. “Efforts should be made to increase doctors’ awareness of the potential negative influence of difficult patients’ behaviors on diagnostic decisions and their ability to counteract such influence.”
New Calculator Provides More Accurate Blood Pressure Estimation
OXFORD, UK – Although blood pressure can be an important tool in determining patient health, it, too, often is a moving target.
To try to remedy that, Oxford University researchers have developed a new way to estimate true underlying blood pressure, overcoming common problems in a clinical setting which can lead to misleading results. Their work, including an online calculator, was published recently in the journal Hypertension.
“One phenomenon where readings are higher in the clinic than at home is referred to as the ‘white coat effect.’ This can lead to people being started on blood pressure-lowering treatments they do not really need,” said study leader James Sheppard, PhD, in a statement. “A reverse effect is also seen — some patients have lower readings in the clinic than they would in normal life, meaning that they can miss out on treatment that they could potentially benefit from. Understanding and accounting for the scale of these home-clinic differences would improve diagnosis and treatment.”
For the study, researchers analyzed data from more than 2,000 patients, focusing on factors such as age, gender, body mass index, alcohol consumption, and tobacco use. They also reviewed blood pressure characteristics from multiple readings taken in clinics, including the difference between the first and last readings and the rate of change in blood pressure among others.
Overall, data from around 900 patients was used to build a model, identifying factors that affect the difference between home and clinic blood pressure readings. The model was then validated by checking the data against other patients in the study.
Resulting from those efforts is a prediction model that uses three separate blood pressure readings taken in a single consultation as well as basic patient characteristics. The model provides an adjusted blood pressure reading touted as significantly more accurate than existing models for identifying hypertension.
“We compared the accuracy of our model to the current UK NICE guidelines and those in use in the USA, Canada, and Europe,” Sheppard said. “It correctly classified 93% of cases, compared to the next best, the NICE guidelines, which correctly classified 78% of patients.”
While correctly classifying patients as hypertensive ensures they get the treatment they need, he added, “Perhaps just as importantly, this approach prevents those patients displaying a white coat effect from being put on treatment which they don't really need.”
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