Basophil Activation Testing Shows Promise in Detecting, Predicting Severity of Food Allergies
New research shows that basophil activation testing (BAT) predicts the severity of food allergies (Ann Allergy Asthma Immunol 2015;114:319–26). BAT is an in vitro study that closely reflects the immunoglobulin E (IgE)-mediated pathophysiology of food allergy. The results support BAT as a tool to enhance discrimination between allergic and non-allergic individuals and potentially as an alternative to time-consuming and risky food challenges.
Double-blind placebo-controlled food challenge is the gold standard for diagnosing food allergies, but is time- and resource-intensive, and can cause severe reactions in some individuals. Prior research with BAT produced promising results, but it “remains an investigational tool,” according to the authors.
This led them to determine whether skin prick testing, allergen-specific and total IgE, allergen-specific IgG4, component testing, and BAT are correlated with outcomes of double-blind placebo-controlled food challenge and the severity of clinical reactions during challenge.
The study involved 67 patients ages 12 to 45 who had a documented history of allergy to peanut, tree nut, sesame, fish, or shrimp, and who were undergoing double-blind placebo-controlled food challenge for enrollment in a separate study. Participants underwent food challenges on separate days for each of the foods in question and had allergen-specific IgE and IgG4, total IgE, and peanut component-specific IgE levels measured, as well as BAT.
In comparison to those with negative food challenge tests, participants with positive food challenge tests had significantly larger skin prick reactions and higher serum IgE levels. In contrast, there were weak or negligible correlations between skin prick tests and serum IgE and food challenge severity.
The researchers used three different concentrations of each allergen to challenge patients’ basophil activation, 200 ng/mL, 2 ng/mL, and 0.02 ng/mL. They found BAT levels significantly correlated with food challenge severity scores at 200 ng/mL, but weakly correlated at 2 ng/mL and 0.02 ng/mL. The area under the receiver operating characteristic curve for the highest dose of BAT was 0.904, in comparison to allergen-specific IgE at 0.87 and skin prick test at 0.765.
While these findings support the utility of BAT in assessing food allergies, the authors aver that there are technical difficulties involved in BAT that challenge its implementation. Basophils are fragile and have short life spans, and the testing remains relatively expensive. The investigators also suggested that more research is needed in understanding basophil differentiation, maturation, migration, and the mechanisms underlying food allergy.
New Mass Spectrometry Method for Detecting Drugs of Abuse in Exhaled Breath
Researchers at the Karolinska Institutet in Sweden reported developing and validating what may be the first liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for detecting drugs of abuse in exhaled breath (J Chromatogr 2015;985:189–96). The method has potential for future use in several fields and provides a procedure not only more convenient for donors but also easier for individuals overseeing test collecting to control, according to the authors.
The investigators developed the method as a response to challenges with urine sample adulteration. “The underlying mechanism in exhaled breath drug testing is believed to be the formation of aerosol particles from the airway lining fluid by the breathing process. These aerosol particles may become contaminated with drugs present in the body, which enables drugs to be highlighted. A simple collection device is currently available which selectively collects the micrometer aerosol particles on a filter and enables further laboratory investigation of possible drug content,” explained the study’s senior author, Olof Beck.
The LC-MS/MS method covers nine analytes, including amphetamine, cocaine, diazepam, and tetrahydrocannabinol with a range of 6.0 to 1,000 pg/filter and intra- and inter-assay coefficient of variation of 7%.
Routine Potassium Screening in Healthy Women Taking Spironolactone Neither Necessary Nor Cost-Effective
Routine potassium monitoring in healthy women taking spironolactone for acne is unnecessary clinically and adds unwarranted healthcare costs (JAMA Dermatol doi:10.1001/jamadermatol.2015.34). The findings should encourage more physicians to prescribe this “highly effective drug,” who, in the past, may have been reluctant to do so because of the perceived need for frequent lab monitoring.
The authors conducted the study because although the Food and Drug Administration recommends frequent potassium monitoring in patients taking spironolactone, it is unclear whether this guidance is really applicable to healthy patients taking the drug for acne. While frequently prescribed as a diuretic and antihypertensive in heart failure, this androgen receptor agonist also counteracts hormonally mediated acne. It also is associated with hyperkalemia in patients with heart failure taking other medications that interfere with potassium excretion. This led the investigators to determine a baseline level of hyperkalemia in young women taking spironolactone for acne.
The researchers conducted a retrospective study of 974 women prescribed spironolactone, as well as 1,165 other healthy women who took or did not take spironolactone. They determined the incidence of hyperkalemia in these populations to be 0.72% and 0.76%, respectively. The authors also compared the cost of spironolactone, $4 per month, with the cost of a single serum potassium measurement, $6.27. However, they noted that clinicians often order a serum electrolyte panel costing $43.51 rather than a single potassium test.
In the study period there were just 13 abnormal serum potassium results among 1,802 measurements, which cost $78,405. Repeat testing in six women with the abnormal values yielded only normal results, suggesting the original measurements were erroneous or transient mild hyperkalemia.
Urine Aquaporin-1, Perilipin-2 Accurately Detect Early Stage Kidney Cancer
A prospective cohort study revealed that urine aquaporin-1 (AQP1) and perilipin-2 (PLIN2) have at least 95% sensitivity and at least 91% specificity for detecting early-stage renal cell carcinoma (RCC) (JAMA Oncol 2015; doi:10.1001/jamaoncol.2015.0213). The findings build on the authors’ prior investigations of AQP1 and PLIN2. AQP1 is a water transport protein found in the kidney proximal tubule; PLIN2 is an adipocyte differentiation-related protein.
The authors conducted the study because while kidney cancer is largely treatable if detected early, most tumors are not detected until later in the disease process when survival rates are lower. At present, population screening for this condition would involve relatively expensive computed tomography or magnetic resonance imaging.
The investigators obtained urine samples from 720 patients who were undergoing routine abdominal computed tomography, 80 healthy controls, and 19 patients with pathologically confirmed RCC. They measured AQP1 via enzyme-linked immunosorbent assay and PLIN2 by Western blot.
The area under the receiver operating characteristic curve for AQP1 and PLIN2 levels individually or in combination was 0.99 or greater, with 95% or greater sensitivity and 91% or greater specificity compared with controls or the screening population. Of the 720 screening population patients, three had AQP1 and PLIN2 concentrations suggestive of RCC.