Paired Comparison Trials Research Articles

Improved detection of house infestations with triatomines using sticky traps: a paired-comparison trial in the Argentine Chaco

BackgroundWe conducted a matched-pairs trial of three methods for detecting house infestation with triatominae bugs in a well-defined endemic rural area in the Argentine Chaco.MethodsThe three methods included a simple double-sided adhesive tape (ST) installed near host resting sites; timed-manual collections with a dislodging aerosol (TMC, the reference method used by vector control programmes), and householders’ bug notifications (HN). Triatomine infestations were evaluated in 103 sites of 54 houses, including domiciles, kitchens and storerooms.ResultsIn domiciles where Triatoma infestans was collected, sensitivity of each single method decreased from 79% by ST and 77% by HN, to 57% by TMC, and increased to 92% when ST was combined with HN. In peridomestic kitchens and storerooms, TMC was relatively as sensitive as ST and significantly more sensitive than HN. On average, the number of bugs recovered by ST was 0.94 times that collected by TMC. The ST mainly collected early-instar nymphs whereas TMC yielded late (larger) stages. Triatomines caught by ST had significantly lower mean weight-to-length ratios and lower blood-feeding rates than those caught by TMC, suggesting the ST intercepted and trapped vectors seeking a blood meal host.ConclusionsThe ST may effectively replace TMC for detecting T. infestans in domiciles, and is especially apt for early detection of low-density domestic infestations in the frame of community-based surveillance or elimination programmes; decision making on whether an area should be targeted for full-coverage insecticide spraying, and to corroborate that extant conditions are compatible with the interruption of vector-borne transmission.

A new method to assess the influence of odor on food selection in dogs

AbstractPrevious research provides evidence that odor is a key driver in food selection in dogs. Dogs' flavor preferences are generally assessed through paired comparison tests based on food intake. Methods for evaluating odor preference in canines are lacking. In this study, the paired comparison test was modified by replacing standard bowls with false‐bottom bowls (FBBs). Made of two compartments separated by a drilled, stainless‐steel plate, FBBs enable odorant compounds to be placed under the food that is presented to the dogs. Several paired comparison trials were conducted on a trained canine panel with FBBs containing various odorant substances under the kibbles. Results showed that dogs were able to perceive the hidden substances and to distinguish between the bowls accordingly. These results demonstrate that the false‐bottom bowl paired comparison method could be helpful in evaluating the role of odor in dogs' food preferences, thus, also as a way of assessing food odor performance.Practical applicationsThe false‐bottom bowl method is an adaptation of the paired comparison test that enables the influence of odor on dog behavior to be isolated from that stimulated by vision, taste or textural parameters. The odor impact of a hidden substance is tested under pet meal conditions. This new method could be useful in pet food industry to measure the odor potential of a new ingredient, or to understand the key food selection drivers for dogs and cats. In addition, as the olfactory stimulus is not eaten by the animal, the influence of odor in non‐food products for dogs, such as pet care and pet medicines, could also be evaluated using this method.

A Paired-Comparision of the MultiFunction CardioGramsm (MCG) and Sestamibi SPECT Myocardial Perfusion Imaging (MPI) to Quantitative Coronary Angiography for the Detection of Relevant Coronary Artery Obstruction (≥70%) - A Single-Center Study of 116 Consecutive Patients Referred for Coronary Angiography

An analysis of the US National Cardiovascular Data Registry has revealed that only 38% of patients referred for coronary angiography after non-invasive coronary testing have relevant coronary obstruction (CO) (≥70%) of one or more coronary arteries. A single-center trial was undertaken in 165 consecutive, symptomatic patients with either known or suspected coronary disease and/or valve disease(VHD) who agreed to undergo cardiac catheterization and coronary angiography if stress myocardial perfusion imaging was abnormal. A total of 116 patients with abnormal SPECT MPI tests, persistent chest pain, or significant VHD underwent final analysis. An MCG coronary obstruction (CO) score of ≥ 4.0 was considered indicative of relevant CO (≥70%) in one or more coronary arteries. Angiographic results were finalized by consensus of two angiographers. CO (≥70%) was present in 53 of 116 patients (46%). The MCG CO score was significantly higher for patients with relevant CO (5.4 ± 1.9 vs. 2.5 ± 1.9). The MCG correctly classified 103 of the 116 patients (89%) enrolled in the study as either having or not having CO (≥70%) (sensitivity- 91%; specificity- 87%; NPV- 92%; PPV- 86%). SPECT MPI was abnormal in 99 of the 116 (85%) patients undergoing catheterization, but correctly classified only 54 of the 116 patients (47%) entered in the study as either having or not having relevant CO (sensitivity-85%; specificity-14%; NPV - 53%; PPV- 45%). The MCG was shown in this paired-comparison trial with SPECT MPI to safely and accurately identify patients with relevant CO (≥70%) prior to catheterization.

Gradient Ascent Subjective Multimedia Quality Testing

Subjective testing is the most direct means of assessing multimedia quality as experienced by users. When multiple dimensions must be evaluated, these tests can become slow and costly. We present gradient ascent subjective testing (GAST) as an efficient way to locate optimizing sets of coding or transmission parameter values. GAST combines gradient ascent optimization techniques with subjective test trials. As a proof-of-concept, we used GAST to search a two-dimensional parameter space for the known region of maximal audio quality, using paired-comparison listening trials. That region was located accurately and much more efficiently than use of an exhaustive search. We also used GAST to search a two-dimensional quantizer design space for a point of maximal image quality, using side-by-side paired-comparison trials. The point of maximal image quality was efficiently located, and the corresponding quantizer shape and deadzone agree closely with the quantizer specifications for JPEG 2000, Part 1.

Infant attention and visual preferences: converging evidence from behavior, event-related potentials, and cortical source localization.

In this study, we had 3 major goals. The 1st goal was to establish a link between behavioral and event-related potential (ERP) measures of infant attention and recognition memory. To assess the distribution of infant visual preferences throughout ERP testing, we designed a new experimental procedure that embeds a behavioral measure (paired comparison trials) in the modified-oddball ERP procedure. The 2nd goal was to measure infant ERPs during the paired comparison trials. Independent component analysis (ICA) was used to identify and to remove eye-movement components from the electroencephalographic data, thus allowing for the analysis of ERP components during paired comparison trials. The 3rd goal was to localize the cortical sources of infant visual preferences. Equivalent current dipole analysis was performed on the ICA components related to experimental events. Infants who demonstrated novelty preferences in paired comparison trials demonstrated greater amplitude Negative central ERP components across tasks than infants who did not demonstrate novelty preferences. Visual preference also interacted with attention and stimulus type. The cortical sources of infant visual preferences were localized to inferior and superior prefrontal cortex and to the anterior cingulate cortex.

Tracking the time to recovery after induced loudness reduction (L)

In induced loudness reduction (ILR), a strong tone causes the loudness of a subsequently presented weak tone to decrease. The aim of the experiment was to determine the time required for loudness to return to its initial level after ILR. Twenty-four subjects were exposed to 5, 10, 20, or 40 brief bursts of 2500-Hz pure tones at 80-dB SPL (inducers) and then tested in a series of paired comparison trials. Subjects compared the loudness of a weak target (2500 Hz at 60-dB SPL) to the loudness of a comparison tone at 500 Hz previously judged to match the target. The comparison task was repeated until the two tones were again judged equally loud. The results showed that (a) recovery after ILR is a relatively long process with a time scale of minutes, and (b) recovery time increased approximately 20 s with each doubling of the number of inducers.

A randomized paired comparison trial of cutaneous treatments for acute jellyfish (Carybdea alata) stings

The objective of the study was to compare cutaneous treatments (heat, papain and vinegar) for acute jellyfish (Carybdea alata) stings. Healthy adult volunteer subjects received a single-tentacle jellyfish sting on each forearm. One forearm was treated with hot-water immersion (40-41°C). This was compared with the other forearm, which was randomized to a comparison treatment of papain meat tenderizer or vinegar. Pain was measured at 0, 2, 4, 6, 8, 10, 15, and 20 minutes using a 10-cm visual analog scale (VAS). For 25 subject runs, the average VAS scores at t = 0 were 3.6 cm (hot water) and 3.7 cm (comparison treatment). At t = 4 minutes (2 minutes after treatment had started), the differences between hot-water and comparison group VAS scores were 2.1 cm versus 3.2 cm, respectively. The mean difference between hot-water and comparison treatments was 1.1 cm (95% confidence interval, 0.6 to 1.6). At t = 20 minutes (the end of the study period), the differences between hot-water and comparison group VAS scores were 0.2 cm versus 1.8 cm, respectively. The mean difference between hot-water and comparison treatments was 1.6 cm (95% confidence interval, 0.9 to 2.3). This study suggests that the most efficacious initial treatment for C alata jellyfish envenomation is hot-water immersion to the afflicted site. (Am J Emerg Med 2002;20:624-626. Copyright 2002, Elsevier Science (USA). All rights reserved.)

The validity and reliability of a portable slip meter for determining floor slipperiness during simulated heel strike

A previously developed test rig was used as starting point for designing a portable slip meter with two new features. First, an inflatable pneumatic test wheel, consisting of six slider units, was introduced as the impacting contact element relative to floor surface. Second, an inductive trigger was built into the system to facilitate a precise timing of the slider-floor contact during the test. This new test rig was designed to measure transitional friction properties of contaminated floor surfaces during simulated heel strike, which is considered the most critical phase of gait from the slip and fall point of view. Another objective was to quantify the validity and reliability of this test method in the laboratory, but not yet in the field. The measurement process was evaluated on eight wet and oily floor surfaces (vinyl and ceramic tile floorings) using two slider materials (plain, profiled), two normal loads (100, 200 N), and two sliding velocities (0.15, 0.30 m/s) as independent variables. The outputs of the portable slip meter, in terms of transitional friction coefficients, were compared to force platform-based friction values and to slip resistance values obtained with a slip simulator apparatus for laboratory testing of shoes and floor surfaces. The outputs were also evaluated against slipperiness ratings made by three male subjects in paired comparison trials, in which the subjects walked over eight wet floor surfaces wearing shoes with the plain soling material. The results showed that test option 200 N and 0.15 m/s led to optimum validity despite its tendency to promote frictional vibrations (stick-slip) in the contact surface. Compared to the lower sliding speed, the higher speed reduced both stick-slip and measurement bias. Test option 200 N and 0.30 m/s was the most reliable one in this experiment. It yielded lower friction coefficients than any other test option and reduced the likelihood of underestimating slip and fall hazards. The results implied that the minimum friction coefficient was 0.25 for preventing a fall on wet floor surfaces, whereas the limit for preventing a slip was in the range 0.30–0.35. Transitional friction measurement was found to be a valid and reliable indicator for slip resistance. A more accurate control of the normal force during testing is needed for actual field use of the test method.

Relevant psychoacoustic parameters in assessments on wind turbine noise

Subjective judgments on wind turbine noise were to determine noise quality parameters which are related to the unpleasantness of noise immissions. In a pre-test paired comparisons of wind turbine noises using headphone presentations showed the superiority of head related recordings compared to single microphone recordings. Loudness contributed mostly to the unpleasantness and masked the contribution of other noise quality parameters. Hence in the main experiment artificial head recordings from a representative set of ten wind turbines were equalized in loudness and judged after their unpleasantness in a complete paired comparison trial by 22 subjects. Insufficient reliability and consistency led to an exclusion of 9 subjects. From the BTL-scaled answers of 13 subjects a factor analysis provided two factors (F1: 71%/F2: 12% of total variance). Means and percentiles of the unweighted, A-, B-, and C-weighted SPL, loudness, roughness, sharpness, fluctuation strength, tonality and impulsiveness were calculated and answers of 11 subjects with high and moderate loads on factor 1 showed significant correlation coefficients with tonality measures (r=0.8 to 0.83). The answers of subjects with high loads on factor 2 significantly correlated with fluctuation strength. No further noise quality parameters turned out to be relevant.

Four-month-olds' recognition of complementary-contour forms

Four-month-old long- and Short-looking infants were habituated to a visual form from which 50% of the contour was removed. Infants were then tested for recognition of the visual form with paired comparison trials in which two other 50%-degraded visual forms were simultaneously presented. One of the two degraded forms presented in the test trials was a novel form, and the other form was comprised of the “complementary contour” (e.i., the contour not previously shown) of the degraded habituation stimulus. Thus, the task involved a testof infants' recognition of a form across stimuli that shared no common contour. Only infants with attentional profiles characterized by shorter fixation durations recognized forms when tested inthis way. These results suggest that some infants are in fact capable of generalizing from one coplementary image to another; the observation of this ability short-looking infants is consistent with previous suggestions of differences in visual encoding as a function of individual differences in fixation duration.

Form categorization in 10-month-olds

In five experiments, 10-month-olds were habituated to exemplars of a form category and tested for categorization in paired-comparison trials involving incategory versus out-of-category stimuli. Across these experiments, color was systematically manipulated during habituation and/or test trials. Infants categorized form when color was either held constant or varied during habituation, but failed to categorize form when exposed to color-constant stimuli during habituation and tested for categorization with novel-color form exemplars. Two subsequent experiments traced this failure to the narrow experience of exposure to color-constant exemplars during habituation. These results suggest that (a) infants' internal representation for a category will not include a stimulus dimension not varied in the exemplars from which the category was derived, but (b) if variation in that dimension is experienced, exemplars constructed of novel instances of that dimension will still be regarded as belonging to the category.

Treatment of scleroderma skin ulcers with a hydrocolloid membrane

The purpose of this study was to determine the usefulness of hydrocolloid membrane dressings in the treatment of finger and hand ulcers of scleroderma (progressive systemic sclerosis). Ten pairs of ulcers occurring in seven patients were studied. The ulcers in each patient were treated in a paired comparison trial: one ulcer in each pair was treated with a hydrocolloid membrane; the other was a control. Treatment was continued until at least one ulcer of each pair was healed. The rate of healing of the hydrocolloid membrane-treated ulcers was significantly faster than that of the control ulcers. Pain was rapidly and dramatically reduced in all hydrocolloid membrane-treated ulcers. An infection caused by Pseudomonas aeruginosa occurred in a hydrocolloid membrane-treated ulcer but rapidly responded to topical therapy. Hydrocolloid membrane treatment of sclerodermatous hand ulcers appears to be an effective method of accelerating healing and reducing pain.

Longitudinal correlates of infant attention in the paired-comparison paradigm

A sample of infants tested on paired-comparison visual discriminations at 4 and 7 months were tested at 16 months on tasks measuring their exploration of a novel environment, short-term spatial memory, and attention span/task persistence. Seven-month novelty preferences were related to accuracy on a spatial memory task, supporting the possibility that memory ability may carry some of the variance in correlations between infant novelty preferences and later intelligence. Also, shifting between targets during paired-comparison trials was related to infants' behavior at 16 months. Shifting at 4 months was positively related to accuracy on the memory task, and at 7 months it was positively related to several exploratory measures, supporting previous contentions that this measure may reflect different processes in early versus late infancy.

Topical Metronidazole Therapy for Rosacea

Forty patients with rosacea were treated topically with 0.75% metronidazole gel in a randomized split-face double-blind paired-comparison trial. With twice-daily applications, 36.7, 48.5, and 65.1 mean percent reductions in total papules and pustules were noted over baseline at 3, 6, and 9 weeks, respectively, on the side of the face receiving metronidazole therapy. Therapy with vehicle alone produced a maximum mean percent reduction of 14.9 at nine weeks. Erythema also responded but was less improved by the end of nine weeks of therapy. A mild increase in telangiectasia was noted on both actively treated and placebo-treated sides. The gel was locally well tolerated. Only two of 40 patients failed to complete the trial, both because of flares of rosacea (one at two days, and one at five weeks). No systemic symptoms were noted, and no consistent abnormalities were found in the results of laboratory studies (hematology, chemistry, and urinalysis). Topical metronidazole gel therapy appears to be a safe and efficacious therapy in the treatment of moderate to severe rosacea.

MULTICENTER TRIAL OF FLUOCINONIDE IN AN EMOLLIENT CREAM BASE

Working independently, eight investigators evaluated the clinical effectiveness of fluocinonide 0.05% in a three-week double-blind paired comparison trial of 240 patients. Half the investigators compared fluocinonide emollient cream with betamethasone valerate 0.1% cream in the treatment of atopic dermatitis, while the remaining four compared the study drug with triamcinolone acetonide 0.1% cream in the treatment of psoriasis. Statistical analysis showed clinical responses favored fluocinonide p = 0.021 (Wilcoxon Signed Rank) for the atopic dermatitis group and p = 0.001 (Wilcoxon Signed Rank) for the psoriasis group.

Social cognition in infants: Attention to the human face

This study investigated infant attention to the human face. A set of stimuli consisting of M other, a S tranger, a manne Q uin, a schematic F ace, and a G eometric stimulus was presented to one-, three-, and five-month-old infants in paired comparison trials in order to examine the influence of familiarity, animation, complexity, and facial configuration on infants' attention. There were several exemplars of each stimulus so that the results generalize beyond specific stimuli. Across several analyses of looking behavior, infants ranked the stimuli, S-M-Q-F-G, indicating that a particular combination of characteristics makes the human face interesting to infants. Infants' ordering of the stimuli was dependent on two factors relating to animation and complexity. Infants at all ages preferred the complex animated faces. The preference for complex and unfamiliar faces increased with age. Relative to other characteristics, facial configuration was not of special importance to infants' attention.

Preference for delay-associated cues: Cognitive dissonance?

Eighteen albino rats were given 96 trials in a runway during which delay-box cues were differentially paired with 2-, 10-, and 30-sec reinforcement delays. The animals then received 18 paired-comparison trials, in a Y-maze, where they were exposed to the three possible pairings of the delay-associated cues. It was found that the animals chose the 2-sec cue significantly more often when paired with either the 15- or 30-sec delay. There was no difference in the frequency of choice for the 10- and 30-sec pairing. Results were discussed with reference to Festinger’s “cognitive dissonance” theory, which predicts a preference for cues associated with longer delays.