PubMed · 10743375
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A Indrayan, P Gupta. Sampling techniques, confidence intervals, and sample size.. https://pubmed.ncbi.nlm.nih.gov/10743375/
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The concept of interchangeable pharmaceutical products has been examined in great detail in the literature. Anderson and Hauck proposed a statistical random coefficient model to study 'switchability', and coined the phrase 'individual bioequivalence' which they defined with a probability-based inequality. Since that paper there has been considerable work and discussion. The Food and Drug Administration has recommended the introduction of individual bioequivalence (IBE) and population bioequivalence (PBE) methods in a draft guidance document. The proposal in the draft guidance includes criteria for IBE and PBE and recommends the use of non-parametric bootstrap 95 per cent upper confidence intervals for the conclusion of either IBE or PBE. However, this method requires intensive computations. We have developed an alternative confidence interval procedure to assess IBE by the FDA recommended criteria. This method utilizes Howe's approximation I to a Cornish-Fisher expansion. Our proposed method is applicable to balanced or unbalanced data in a broad class of extended cross-over designs, and can be easily programmed using readily available software.
OBJECTIVE: To compare rates of local reactions associated with two needle sizes used to administer routine immunisations to infants. DESIGN: Randomised controlled trial. SETTING: Routine immunisation clinics in eight general practices in Buckinghamshire. PARTICIPANTS: Healthy infants attending for third primary immunisation due at 16 weeks of age: 119 infants were recruited, and 110 diary cards were analysed. INTERVENTIONS: Immunisation with 25 gauge, 16 mm, orange hub needle or 23 gauge, 25 mm, blue hub needle. MAIN OUTCOME MEASURES: Parental recordings of redness, swelling, and tenderness for three days after immunisation. RESULTS: Rate of redness with the longer needle was initially two thirds the rate with the smaller needle (relative risk 0.66 (95% confidence interval 0.45 to 0.99), P=0.04), and by the third day this had decreased to a seventh (relative risk 0.13 (0.03 to 0.56), P=0.0006). Rate of swelling with the longer needle was initially about a third that with the smaller needle (relative risk 0.39 (0.23 to 0.67), P=0.0002), and this difference remained for all three days. Rates of tenderness were also lower with the longer needle throughout follow up, but not significantly (relative risk 0.60 (0.29 to 1.25), P=0.17). CONCLUSIONS: Use of 25 mm needles significantly reduced rates of local reaction to routine infant immunisation. On average, for every five infants vaccinated, use of the longer needle instead of the shorter needle would prevent one infant from experiencing any local reaction. Vaccine manufacturers should review their policy of supplying the shorter needle in vaccine packs.
Chronotropic incompetence, or an attenuated heart rate response to exercise, has been shown to be associated with an adverse outcome. It is not known whether chronotropic incompetence predicts all-cause mortality independent of angiographic severity of coronary artery disease (CAD). Study subjects included consecutive patients who underwent first-time, symptom-limited exercise treadmill testing and coronary angiography within 90 days; no patient was taking beta blockers or had a history of heart failure, valve disease, or prior revascularization. Chronotropic response was measured in 2 ways: (1) failure to reach 85% of the age-predicted maximum heart rate, and (2) a low chronotropic index, a measure of exercise heart rate response that accounts for effects of age, physical fitness, and resting heart rate. Angiographic severity of CAD was assessed using the Duke Prognostic Weight Score, with a score > or = 42 considered to be indicative of severe CAD. Among 384 eligible patients, failure to reach 85% of the age-predicted maximum heart rate occurred in 61 (16%) and a low chronotropic index was noted in 133 (35%). Severe CAD was present in 63 (16%). During 6 years of follow-up there were 56 deaths. Mortality was predicted by failure to reach target heart rate (RR 1.85, 95% confidence interval [CI] 1.01 to 3.39, chi-square = 4, p = 0.05), by severe CAD (RR 2.21, 95% CI 1.24 to 3.95, chi-square = 8, p = 0.007), and, most strongly, by a low chronotropic index (RR 2.72, 95% CI 1.60 to 4.61, chi-square = 15, p = 0.0002). In a multivariable model, low chronotropic index remained predictive of death (adjusted RR 2.22, 95% CI 1.29 to 3.82, p = 0.004), whereas severe CAD no longer predicted death (adjusted RR 1.27, 95% CI 0.70 to 2.31, p > 0.4). Thus, chronotropic incompetence is a strong and independent predictor of death, even after accounting for the angiographic severity of CAD.