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PubMed1987

Blinding, unblinding, and the placebo effect: an analysis of patients' guesses of treatment assignment in a double-blind clinical trial.

We administered a questionnaire to assess maintenance of patients' blindness at the end of a double-blind clinical trial of Osmotic Release Oral System phenylpropanolamine (PPA) vs. placebo in mild obesity. Seventy-four percent of placebo participants and 43% of PPA participants guessed their treatment correctly. Appetite control was the most frequently reported basis for guessing PPA, even by placebo participants. Lack of adverse drug reactions was the most frequently reported basis for guessing placebo, even by PPA participants. Participants receiving either PPA or placebo and guessing PPA lost more weight, had less diet difficulty, and had more adverse drug reactions than had participants receiving either PPA or placebo and guessing placebo. Although blindness was probably maintained in the PPA group, the placebo group seems to have been, at least at the study's end, unblinded. These results suggest that in double-blind studies, differences in outcome or incidence of adverse drug reactions may act as unblinding factors.

Body Weight↗

PubMed1988

Effect of topical levocabastine on allergic and non-allergic perennial rhinitis. A double-blind study, levocabastine vs. placebo, followed by an open, prospective, single-blind study on beclomethasone.

Forty-four patients, with symptoms of nasal obstruction, sneezing, itching and/or rhinorrhea, were entered into a placebo-controlled, double-blind study to evaluate the clinical efficacy of a topical antihistamine drug, levocabastine, applied 4 times a day for 14 days. At the end of the treatment the placebo patients were treated with levocabastine and the levocabastine patients were treated with beclomethasone dipropionate in a single-blind design for another 14 days. This study showed that levocabastine is significantly more active than placebo with reference to nasal discharge and sneezing. Placebo application improved the symptom score. Levocabastine could not be proved to be more effective against nasal obstruction than placebo in the double-blind trial. In the single-blind set-up, levocabastine resulted in an additional improvement in the score for obstruction, after the placebo period. Although the allergic group tended to respond better, no statistically significant difference could be detected between allergic and non-allergic patients. After treatment with levocabastine, beclomethasone dipropionate administration could not improve the results for nasal discharge and sneezing. For nasal congestion, beclomethasone dipropionate proved to be superior to levocabastine.

Administration, Intranasal↗

PubMed1976

Causes of blindness among students in blind school institutions in a developing country.

Out of 270 students in 17 blind school institutions in Malawi 73 per cent were blind before the age of three. The most common cause for the blindness was ocular infection (75-2 per cent). Meales, as a single cause, was responsible for 43-7 per cent of the cases and smallpox for 5-2 per cent. Bacterial infections were incriminated in 26-3 per cent of the cases. Most of these had received traditional medicine during the acute phase of the disease. Hereditary factors as causes of blindness were found in 7-8 per cent of the cases. These included congenital cataracts (2-6 per cent), optic atorphy of unknown origin (3-0 per cent), microphthalmos (1-5 per cent), and macular degeneration (0-7 per cent). Careful ophthalmological examination showed that in 37 cases an intervention could be attempted in order to improve the vision. In the 11 most favourable cases this was attempted, with the result that nine cases gained a useful vision of 4/60 to 6/18 in the better eye.

Adolescent↗

PubMed1990

3.8 million blinded by cataract each year: projections from the first epidemiological study of incidence of cataract blindness in India.

Data from a population based longitudinal study of randomly selected communities in Central India have for the first time provided direct estimates of age specific incidence of blindness from cataract. Person-time denominators have been used to compute age specific incidence rates (risk) of blindness from cataract for populations aged 35 and older. These age specific incidence measures have been applied to the 'population at risk' in each 5-year age class in order to estimate the total number of new cases of cataract blindness that occur in the country each year. The findings indicate that an estimated 3.8 million persons become blind from cataract each year in India (approximate 95% confidence limits: 3 to 4.5 million). The reasons why the estimates are considered as minima, and their implications concerning future national planning of ophthalmic services, are briefly discussed.

Adult↗

PubMed1975

Experimental production of elevated serum folate in dogs with intestinal blind loops. II. Nature of bacterially produced folate coenzymes in blind loop fluid.

Jejunal and ileal blind loops were constructed in separate groups of dogs and the folate coenzymes present in these loops were investigated. Although only those dogs with high blind loops had appreciably elevated folate levels active for Lactobacillus casei but not Streptococcus faecalis, every blind loop appeared to contain four folate compounds--5-formyltetrahydrofolic acid, 5-methyltetrahydrofolic acid, tetrahydrofolic acid and a compound tentatively identified as 5-formyltetrahydrofolic triglutamate. Why increased levels of 5-methyltetrahydrofolate alone are present in the serum of dogs with a high blind loop is discussed.

Animals↗

PubMed1992

Ultrastructural changes of the retina and the retinal pigment epithelium in Briard dogs with hereditary congenital night blindness and partial day blindness.

The offspring of two Briard dogs (brother and sister) with congenital, clinically stationary night blindness showed an aggravation of the disease with severe impairment of day vision in addition to night blindness. This ultrastructural study was performed on four such second generation puppies at the age of 4 months. The neuroretina and retinal pigment epithelium (RPE) from four locations were studied: the central area (immediately temporal to the optic disc); the centre of the tapetal area; the upper periphery (border of tapetal area); and the lower periphery (non-tapetal area). The RPE showed large inclusions, seemingly lipid in nature, mainly in the central and tapetal areas of the retina. Small, membrane bound, electron-dense inclusions were scattered in the RPE cytoplasm in all areas examined. The small inclusions were found to be less numerous in normal than in affected dogs and may be lysosomal in nature. Forty to fifty percent of the rod outer segments in the tapetal area showed disorientation of the disc membranes, whereas the corresponding figures were 20-40% in the central and lower peripheral areas and 6-25% in the upper peripheral area. No structural abnormalities were found in the rod inner segments or synaptic bodies. The cones were better preserved. The inner retina appeared normal. These electron microscopic findings seem to correspond to a previously published electrophysiologic evaluation, indicating a defective and delayed rod function (virtually no scotopic a- and b-waves), a better preserved cone function (photopic flicker responses present, although reduced) and impaired RPE activity (a prominent, slow negative potential of long latency at the site of the c-wave). It appears that these Briard dogs, showing structural changes of the rod outer segments in addition to pigment epithelial inclusions, mainly located in the posterior pole, comprise a pigment epitheliopathy and retinopathy morphologically different from other hereditary canine retinopathies that have been described earlier in the literature and different from animal models of congenital night blindness.

Animals↗

PubMed1991

Comparison of response rates to the angiotensin-converting enzyme inhibitor ramipril in mild-to-moderate hypertension in a double-blind, parallel-group study and an open single-blind study.

Appropriate clinical trial methodologies in general practice and suitable end points for dose-finding studies are discussed with reference to antihypertensive drugs in general and angiotensin-converting enzyme (ACE) inhibitors in particular. Two clinical studies were conducted with ramipril, a new nonsulfhydryl ACE inhibitor, to identify the minimum effective dose for the management of mild-to-moderate hypertension. Study 1 was a double-blind, parallel-group, randomized design with three treatment groups (placebo and 2.5 and 5 mg of ramipril), and study 2 was an open, single-blind design with individual dose titration from 2.5 to 5 mg of ramipril if the diastolic blood pressure (DBP) was greater than 90 mm Hg after 3 weeks. Response rates and DBP reductions with 2.5 mg of ramipril were similar in both studies, although overall response rates, DBP reductions, and side effect incidence appeared to be greater in the open, single-blind, dose-titration study. It is concluded that study methodology apparently influences efficacy and tolerability.

Angiotensin-Converting Enzyme Inhibitors↗

PubMedDate not supplied

Rod densitometry in night blindness: a review and two puzzling cases. Rod densitometry in night blindness.

Since the non-invasive technque of retinal densitometry became available in 1955, rhodopsin kinetics could be studied in vivo. It was obvious that with this new tool investigators focussed attention on the aetiology of night blindness in various diseases. A brief review about the clinical developments in the past two decades is given. Also three case-reports are presented, which suggest that in some cases of congenital stationary night blindness (CSNB) the night blindness might arise from the absence of rhodopsin. This is contrary to the standing opinion and present problems regarding the integrity of the retina.

Adolescent↗

PubMed1991

How "blind" are double-blind studies?

Psychopharmacological studies usually attempt to eliminate "nonspecific" influences on outcome by double-blind designs. In a randomized, double-blind comparison of alprazolam, imipramine, and placebo, the great majority of panic disorder patients (N = 59) and their physicians were able to rate accurately whether active drug or placebo had been given. Moreover, physicians could distinguish between the two types of active drugs. Inasmuch as correct rating was possible halfway through treatment, concerns about the internal validity of the double-blind strategy arise.

Adult↗

PubMed1988

Long day photoperiods and temperature of 20 degrees C induce spermatogenesis in blinded and non-blinded marbled newts during the period of testicular quiescence.

Adult male marbled newts (Triturus marmoratus) were collected at the end of the spermatogenesis period and exposed to different photoperiods (natural-daylength-simulated photoperiod, total darkness, 8L:16D, 12L:12D, 16L:8D, and continuous light) for 3 mo. Temperature was maintained at 20 degrees C. Two additional groups of newts were blinded and exposed to either the natural-simulated photoperiod and to 16 h of light per day respectively. Quantitative histologic studies on testicular development and germ cell volume per testis were performed. The newts captured in the field at the beginning (initial controls) or at the end of the experiments (final controls) were in the period of testicular quiescence. Newts kept in total darkness or exposed to a short photoperiod (8L:16D) showed germ cell development up to primary spermatocytes, whereas germ cell development in the newts exposed to long photoperiods (12L:12D or 16L:8D) progressed to elongated spermatids. The newts exposed either to intermediate photoperiods (natural-simulated photoperiod) or to constant light showed an intermediate degree of germ cell development (up to round spermatids). No significant differences between non-blinded and blinded animals were found. These results suggest that (1) mild temperature initiates testicular development in the period of testicular quiescence, (2) long photoperiods associated with mild temperatures produce spermatogenesis in this period, (3) complete darkness or constant light are less effective than some intermediate photoperiod, and (4) the effect of photoperiod on testicular function in newts is not related to ocular photoreception.

Animals↗

PubMed1988

Acute idiopathic blind spot enlargement. A big blind spot syndrome without optic disc edema.

We examined seven patients who had a syndrome of symptomatic monocular blind spot enlargement without optic disc edema. Two patients had previous blind spot enlargement that resolved over several months. The scotoma in each patients was absolute, measured 15 degrees to 20 degrees in diameter, had steep geographic margins, and extended to within 5 degrees to 10 degrees of fixation. Typically, patients had normal visual acuity, color vision, pupillary responses, and ophthalmoscopic findings. Photostress recovery, tested in two patients, was prolonged in the affected eye. Fluorescein angiography showed no abnormalities corresponding to the scotoma. Orbital computed tomographic scans in three patients and visual evoked responses in one patient were normal. Multifocal electroretinography, performed in two patients, showed loss of retinal waveforms in a large region surrounding the optic disc. Our findings suggest that retinal dysfunction produces this big blind spot syndrome, but we do not know its cause.

Acute Disease↗

PubMed1976

Spirometric comparison of carbuterol and isoproterenol aerosol therapy in bronchial asthma. A double blind, matched-pair study of 28 adults and a double blind crossover study of 18 children.

Two adrenergic aerosols were compared in a double blind, matched-pair study of 6 months' duration in 28 adult patients with chronic bronchial asthma, and in a double blind, crossover, short-term study in 18 children with severe asthma. In the adult study, one member of each pair was given either 150 mug of isoproterenol or 200 mug of carbuterol 4 times per day, by inhalation, for 6 months. In the childhood study, 18 children, 6 to 12 years of age, with moderate to severe asthma were studied in a double blind, crossover therapeutic trial in which high or low doses of aerosolized carbuterol or isoproterenol were given 4 times daily for 5 days each. Treatment results were evaluated by measuring forced vital capacity, 1-sec forced expiratory volume, and maximal mid-expiratory flow (FEF25-75%) at regulat intervals before and after administration of the respective test drugs. In the adult study, there was a significant difference between carbuterol and isoproterenol for forced vital capacity (P less than 0.02), for 1-sec forced expiratory volume (P less than 0.02), and for FEF25-75% (P less than 0.01) in favor of carbuterol. In the pediatric study, the difference between carbuterol and isoproterenol was significant (P less than 0.05) only for the FEF25-75% on the fifth day of treatment with the high dose administration of carbuterol. There was no associated toxicity of either drug with respect to electrocardiogram, blood chemistry, or subjective complaints. Tachyphylaxis (tolerance with time) to isoproterenol appeared to develop in one patient.

Adrenergic beta-Agonists↗

PubMed1992

Prospective randomized open blinded end-point (PROBE) study. A novel design for intervention trials. Prospective Randomized Open Blinded End-Point.

A novel design for intervention studies is presented, the so called PROBE study (Prospective Randomized Open, Blinded End-point). This design is compared to the classical double-blind design. Among the advantages of the PROBE design are lower cost and greater similarity to standard clinical practice, which should make the results more easily applicable in routine medical care. Since end-points are evaluated by a blinded end-point committee it is obvious that there should be no difference between the two types of trials in this regard.

Blood Pressure↗

PubMed1991

[Blind ending bifid ureter with stone in the blind branch: report of a case].

Blind ending bifid ureter is a rare anomaly in the urinary tract. This anomaly may result from failure of a premature branch of the ureteral bud to join with the metanephric blastema. A 21-year-old man was admitted with macroscopic hematuria and colic pain in the left flank region. Urinalysis demonstrated hematopyuria and excretory urography suggested bifid ending accessory ureter with a stone on the left side. Surgical exploration showed that the accessory ureter was bifurcated from the left ureter at about 5 mm from the bladder wall and ran parallel with the left ureter. Although dense adhesions to the surrounding tissue existed, the accessory ureter was resected at the site of the junction. It measured 3 cm in length and 1 cm in greatest diameter. The stone found at the tip of the accessory ureter was composed of calcium oxalate (24%) and calcium phosphate (76%). Histological examination revealed that the ureter had all layers of normal ureteral structure and no renal tissue was identified in the specimen resected. During a follow-up period of 22 months after the operation, he was free of urinary tract infection and abdominal pain. Of 77 cases with blind ending bifid ureter reported in the Japanese literature, a ureteral stone was found in the blind branch in only 5 cases.

Adult↗

PubMed1979

Double-blind and triple-blind assessments of medication and placebo responses in hyperactive children.

Hyperactive boys taking psychostimulant medication were studied using a randomized, placebo-controlled, crossover design. Behavior ratings and medication guesstimates were obtained for the boys when they were given methylphenidate (Ritalin) and when they were given a placebo. The ratings showed positive medication-related changes, and the guesses, done by independent judges, were significantly better than chance. The pattern of ratings for double-blind and triple-blind raters was identical. These results imply that positive psychostimulant effects are not attributable to rater sensitization or expectancy. The medication-placebo differences were highly reliable for the group comparisons and were in the predicted direction for 21 of 22 individuals, but the magnitude of the change for many individuals was not dramatic. Implications for child psychopharmacology research and differences between clinical and experimental significance are discussed.

Child↗

PubMed1975

Blindness in Mentally Retarded Children. A survey of the causes of blindness in 201 notified patients.

A preliminary survey of the causes of blindness in mentally retarded children in Denmark showed that 50% of the children had optic atrophy, 12.5% had cataract while tapeto-retinal degenerations, other malformation and retrolental fibroplasia each represents 8-9% of the causes of blindness. The survey, was done through written notification and some patients with tapeto-retinal degenerations might have been wrongly diagnosed.

Blindness↗

PubMed1991

A combined single-blind, double-blind, placebo-controlled study to determine the reproducibility of hypersensitivity reactions to aspartame.

Aspartame is an O-methyl ester composed of phenylalanine and aspartic acid. After its final approval as a sweetener in 1981, a number of reports of adverse reactions to aspartame appeared in the literature. To explore the pathogenesis of such reactions, we initiated a study in July 1986 to identify subjects with hypersensitivity reactions to aspartame with blinded challenge procedures. The study was closed after 32 months. During that time, we advertised in local newspapers and worked closely with the local community of allergists and dermatologists in an attempt to recruit subjects with hypersensitivity reactions to aspartame. A total of 61 self-referrals and physician referrals were screened, with 20 referrals evaluated in clinic. After this evaluation, 12 patients underwent single- and double-blind challenge with up to 2000 mg of aspartame. No subject with a clearly reproducible adverse reaction to aspartame was identified. In summary, we found that it is difficult to recruit study subjects with a history of hypersensitivity reactions to aspartame and that subjects who believed themselves allergic to aspartame did not have reproducible reactions.

Adult↗

PubMed1992

Changes in the DC electroretinogram in Briard dogs with hereditary congenital night blindness and partial day blindness.

Five Briard dogs, 7-12 months old, with congenital night blindness and severely reduced day vision (offspring of a sister and brother with congenital and supposedly stationary night blindness but with normal or nearly normal day vision) and three normal control dogs were studied by means of direct current (DC) electroretinography in order to analyse fast and slow retinal and pigment epithelial (RPE) potentials. No definite a- and b-waves were seen in the affected dogs in the dark-adapted state, which indicates severely impaired rod function. All affected dogs responded to 30 Hz flickering light in the light-adapted state, although with an amplitude reduced by 50-70%. Thus, cone function was better preserved than rod function. The control dogs showed a small c-wave and a deep negative trough between the b- and c-waves, indicating that slow PIII from the Müller cells, as well as the photoreceptor potential, are very prominent. In the affected dogs, there was no c-wave, but from a stimulus intensity of 3 log U above the normal b-wave threshold, a slow negative potential appeared, the latency and peak time of which were very long, 5-7 and 11-15 sec, respectively. With increasing stimulus intensities, both parameters decreased substantially, whereas the amplitude increased to a maximum of 2400 microV. In the light-adapted state, the dog with the best day vision showed a negative potential of short duration (peak time about 0.2 sec), followed by a positive potential (peak time about 1.2 sec).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗