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Simple sample size calculation for cluster-randomized trials.

BACKGROUND: Cluster-randomized trials, in which health interventions are allocated randomly to intact clusters or communities rather than to individual subjects, are increasingly being used to evaluate disease control strategies both in industrialized and in developing countries. Sample size computations for such trials need to take into account between-cluster variation, but field epidemiologists find it difficult to obtain simple guidance on such procedures. METHODS: In this paper, we provide simple formulae for sample size determination for both unmatched and pair-matched trials. Outcomes considered include rates per person-year, proportions and means. For simplicity, formulae are expressed in terms of the coefficient of variation (SD/mean) of cluster rates, proportions or means. Guidance is also given on the estimation of this value, with or without the use of prior data on between-cluster variation. CASE STUDIES: The methods are illustrated using two case studies: an unmatched trial of the impact of impregnated bednets on child mortality in Kenya, and a pair-matched trial of improved sexually-transmitted disease (STD) treatment services for HIV prevention in Tanzania.

Child, Preschool↗

Calcium supplementation and prevention of pregnancy induced hypertension.

In a randomized controlled trial 201 healthy nulliparous women were randomly allocated by means of a computer generated randomization list. From 20 weeks of gestation until delivery they received either 2 g of oral elemental calcium (n = 103) per day or an identical placebo (n = 98). Eleven women (5.47%) were lost to follow-up after randomization. The study groups were very similar at the time of randomization; with respect to several clinical and demographic variables. Treatment compliance was very similar in both groups as was determined by pill count. The rate of pregnancy induced hypertension was lower in the calcium group than in the placebo group 8.24%; vs 29.03%; (RR = 0.28; 95% CI 0.14-0.59). The incidence of gestational hypertension was 6.18% in the calcium group and 17.20% in the placebo group (RR = 0.28; 95% CI 0.08-0.80), and the incidence of preeclampsia was 2.06% in the calcium group and 11.82% in the placebo group (RR = 0.13; 95% CI 0.01-0.64). In conclusion calcium supplementation given in pregnancy to nulliparous women reduces the incidence of pregnancy induced hypertension.

Calcium↗

Differential effectiveness of telephone prompts by medical and nonmedical staff in increasing survey response rates: a randomised trial.

We conducted a randomised trial to determine the differential effectiveness of a telephone prompt by a medical researcher compared with a nonmedical research assistant in improving response rates of general practitioners to a survey and to compare personnel costs. A national random sample of Australian general practitioners was allocated randomly to two intervention groups. In advance of a self-administered questionnaire, Group A (n = 184) received a telephone prompt by a medical researcher and Group B (n = 189) a prompt by an experienced nonmedical research assistant. Other aspects of survey administration were identical for both groups. The five-month cumulative response rate obtained by the medical researcher (81 per cent) was not significantly different from that of 72 percent obtained by the research assistant (chi 2 = 3.3, 1 df, P = 0.07). For Group A, 279 telephone calls, consuming 23 hours 15 minutes, were made. Group B required more calls (384) and more time (32 hours). Using the relevant award pay scales, the estimated personnel costs for each group were $631 and $601 respectively. We conclude that an experienced nonmedical research assistant is as effective as a medical practitioner in administering telephone prompts to enhance survey response rates, although savings are not necessarily made.

Costs and Cost Analysis↗

Adding ketoprofen to intravenous patient-controlled analgesia with tramadol after major gynecological cancer surgery: a double-blinded, randomized, placebo-controlled clinical trial.

Ketoprofen is a NSAIDs of the 2-aryl propionic acid class commonly used in the treatment of inflammatory rheumatic disease, acute pain and fever. Clinically, ketoprofen seems to reduce morphine requirements by 33 to 40% with ketoprofen's supposed central mechanism of analgesia. We evaluated the efficacy and safety of intravenous (IV) ketoprofen as an adjuvant to IV PCA (patient controlled analgesia) with tramadol after major gynecological cancer surgery for postoperative analgesia. Fifty patients were enrolled in this double-blinded, randomized, placebo-controlled study. Patients were allocated randomly to two groups: group I (25 patients) served as a control group, with patients receiving saline; group II (25 patients) received ketoprofen. Patients received an intravenous bolus of saline or 100 mg ketoprofen at the end of surgery. Then, PCA was given as a 20 mg tramadol bolus and 10 min lockout time. Pain relief was regularly assessed using a visual analog scale. Tramadol consumption, side-effects, and patient satisfaction were noted during the 24 hours after the surgery. No significant difference was observed in pain score, side-effects and patient satisfaction between the groups (p > 0.05). The cumulative PCA-tramadol consumption was lower in the ketoprofen-treated patients than placebo-treated patients (p < 0.05). Our results demonstrate that a single dose of 100 mg ketoprofen reduced tramadol consumption for treatment of postoperative pain after major gynecological cancer surgery.

Abdomen↗

Physiotherapy and intermittent positive-pressure ventilation of chronic bronchitis.

Patients aged over 45 admitted to hospital with exacerbations of chronic bronchitis alone or in association with cor pulmonale, pneumonia, or respiratory failure were placed in one of three groups (men with hypoxia, men without hypoxia, and women). Patients within these groups were then randomly allocated to receive either standard drug treatment alone or standard drug treatment plus intermittent positive-pressure ventilation (IPPV). No significant differences occurred between the controls and patients receiving physiotherapy and IPPV in any group. We conclude that when a patient with chronic bronchitis and respiratory failure is deteriorating emphasis should be on correct diagnosis, fluid electrolyte balance, and nutrition together with oxygen treatment when necessary, rather than on additional physiotherapy.

Aged↗

Effectiveness of thymostimulin treatment in hepatitis B surface antigen-positive chronic active liver disease. Results of a randomized clinical trial.

The results of this controlled trial with thymostimulin (TP-1 Serono) on hepatitis B surface antigen (HBsAg)-positive chronic active liver disease (CALD), involving 34 consecutive patients chosen by predefined criteria and randomly allocated to control and treatment groups, show that this thymic hormone may significantly improve the clinical, biochemical, serological and immunological parameters of this disease, and ameliorate the quality of the patients' life. The treatment schedule was adjusted according to the immunological response. Our study population was too small to enable any conclusions to be drawn: further studies are therefore required to establish the exact role of thymostimulin in the treatment of HBsAg-positive CALD.

Adult↗

The use of a bladder pressure warning device during transurethral prostatic resection decreases absorption of irrigation fluid.

During a period of 4 weeks 102 patients underwent transurethral prostatic resection (TURP). Of these, 50 were randomly allocated to the use of an intravesical pressure device which warned the surgeon at a pressure elevation of 1.5 kPa. Ethanol (1%) was used as a marker in the irrigation fluid (glycine 2.2%), and absorption of ethanol-tagged irrigation fluid was detected by measurements in the expired air. In 28 patients absorption took place (in 8 of the 50 patients equipped with the warning device and in 20 of the 52 without the device). The greatest absorption was seen in the group without the device. No differences were found between the groups with regard to age, resected mass, resection time, resection speed, or haemorrhage. Patients who absorbed irrigation fluid were slightly older and bled more, and the resected mass was larger. The use of a pressure warning device reduces the amount of irrigation fluid absorbed and the number of patients who absorb irrigation fluid, and minimises the risk of the TUR syndrome.

Absorption↗

Psychological effects of day case surgery compared with inpatient surgery.

Short term psychological disturbance in 70 children undergoing minor surgery was compared in two randomly allocated groups by means of questionnaires answered by their parents. Significantly less psychological disturbance was reported in children undergoing day case surgery compared with children admitted on the day before and discharged on the day after surgery. Children who had day case surgery were less often reported to require extra attention in the first week after discharge home, and at three months after operation these children were less often said to be still affected by their hospital stay. It is concluded that a reduced psychological upset can now be added to the other arguments in favour of day case surgery in children.

Ambulatory Surgical Procedures↗

Extradural analgesia: the influence of volume and concentration of bupivacaine on the mode of delivery, analgesic efficacy and motor block.

Five hundred and seventeen women in labour receiving extradural analgesia, using bupivacaine plain solution, were randomly allocated to one of three groups. Group A received 6-8ml of 0.5% solution, group B 10-14ml of 0.25% solution, and group C 6-8 ml of 0.25% solution. Spontaneous delivery occurred in 31.7% of patients in group A, 38.7% in group B and 53% in group C (P less than 0.001). The percentage of rotational forceps, ventouse and Caesarean section deliveries was similar in the three groups. Analgesia was most effective in group A, and at least in group C, both during labour and at delivery, although assessment by linear analogue score suggested that the differences between the three groups were slight. Motor block was most frequent and rapidly progressive in groups A, but was progressive in all groups, and after five or more top-up injections, was similar in the three groups. Difficulties with micturition following delivery were significantly more common in group A.

Adult↗

Bumetanide, spironolactone and a combination of the two, in the treatment of ascites due to liver disease. A prospective, controlled, randomized trial.

There are few studies available comparing the efficacy of loop and distal diuretics and a combination of the two groups, in the treatment of ascites due to liver disease. Thirty-seven nonazotemic cirrhotic patients with ascites were randomly allocated to receive for 2 weeks bumetanide (group A, n = 13), spironolactone (group B, n = 12) or a combination of the two drugs (group C, n = 12) after a 5-day stabilization period. The response to the treatment was 69, 42 and 83% in groups A, B and C, respectively; the difference was not significant. Hypokalemia was seen in 4 patients of group A and mild hyperkalemia in 2 patients of group B. Electrolyte disturbances were minimal in patients of group C. The response to diuretic treatment was prompt in groups A and C. It can be concluded that a combination of loop and distal diuretics is superior to a one-drug regimen in achieving a rapid and better diuretic response with fewer side effects.

Administration, Oral↗

A pilot study of recombinant interleukin-2 for treatment of chronic hepatitis C.

The optimal and safer interleukin-2 (IL-2) dose for treatment of chronic hepatitis C virus (HCV) infection has been studied in 33 HCV-RNA positive patients with chronic hepatitis C. Patients were randomly allocated to receive 5 days per week during 12 weeks IL-2 doses of: 0.9 MIU (n = 10), 1.8 MIU (n = 10), or 3.6 MIU (n = 13). After 12 weeks, responder patients stopped treatment, whereas nonresponders received 12 additional weeks of IL-2 at the next higher dose: 1.8, 3.6, or 5.4 MIU. As a whole, after the first 12 weeks of IL-2 alanine aminotransferase (ALT) levels significantly decreased (P < .001) with respect to the baseline values (140 +/- 63 vs. 70 +/- 30 IU/L). At the end of treatment (24 weeks), the mean ALT level (80 +/- 50 IU/L) continued significantly lower (P < .001) than the baseline one, and 24% of patients normalized ALT levels; according to dosage, ALT normalization was: 0% for 0.9 MIU, 25% for 1.8 MIU, 5% for 3.6 MIU, and 18% for 5.4 MIU. HCV-RNA levels decreased during treatment, but in none of the patients became undetectable. All patients had a local reaction at the injection site with induration, erythema, and swelling, which was dose-related. The dose of 5.4 MIU was poorly tolerated and was reduced to 3.6 MIU in 4 of 11 patients. No changes in hematological parameters were observed. At the end of follow-up (6 months) four of eight responder patients continued with normal ALT. In conclusion, IL-2 treatment for chronic hepatitis C induced a biochemical response in 8 of 33 (24%) patients at the end of therapy while at the end of follow-up, 4 of 33 (8%) patients remained with normal ALT. The dose of 1.8 MIU is well tolerated and seems to be the most efficacious.

Adult↗

A controlled study of short-term prednisone treatment in adults with membranous nephropathy.

Seventy-two adults with the nephrotic syndrome without renal insufficiency had a membranous type of renal histology on biopsy. These patients were randomly allocated to at least eight weeks of alternate-day treatment with prednisone or placebo in a multicenter study. Deterioration of glomerular filtration rate was significantly more rapid in placebo-treated than in prednisone-treated patients, and ultimately 10 of 38 given placebo but only one of 34 given prednisone were in renal failure (creatinine more than 5 mg per deciliter [440 mumol per liter]) or dead (P less than 0.02). In male patients and in those with nonselective initial proteinuria, there was a trend (not reaching statistical significance) toward more rapid deterioration of renal function. Age, admission blood pressure, serum creatinine, daily total protein excretion, and severity of histologic changes did not predict the subsequent course. We conclude that a short course of alternate-day prednisone therapy was beneficial in our group of patients with idiopathic membranous nephropathy.

Adolescent↗

Lorazepam in children. A double-blind trial comparing lorazepam, diazepam, trimeprazine and placebo.

One hundred patients aged 5-13 yr were randomly allocated to four groups in a double-blind study of premedication. Drugs studied were lorazepam, diazepam and trimeprazine. A placebo group was included. All the drugs appeared satisfactory as premedicants. Lorazepam induced the most sedation immediately after surgery, but by 4 h lorazepam and diazepam appeared similar. Lorazepam produced better amnesia than the other drugs. There were no untoward side-effects and no cardiorespiratory depression in any group. Lorazepam appears a suitable premedicant for children.

Adolescent↗

[Importance of oral rehydration in acute infantile diarrhea. Comparison of 2 rehydration solutions].

Oral rehydration therapy has gained worldwide acceptance as the standard treatment for acute diarrhoeal diseases in infants and children. Besides the high sodium glucose-electrolyte solution based on the WHO/UNICEF recommendations, many diverse formulations of oral rehydration solutions (ORS) have withstood the trial of prolonged clinical use, their main differences concerning the concentration of sodium, the choice of the glycidic component, the use of bicarbonate as buffer or its substitution with acetate or citrate. It was recently hypothesized that glucose polymers-containing ORS markedly improve the intestinal sodium/glucose cotransport by delivering glucose at its critical site on the luminal villous membrane and therefore diminish stool output and duration of the diarrhoea. To investigate this hypothesis, the efficacies of two marketed ORS (table I), one containing sucrose and maltodextrin (solution A) and the other containing glucose (solution B) were compared. The study group comprised 13 infants and toddlers, 1 to 18 months old, who presented with acute diarrhea; 5 were males and 8 females; 7 were randomly allocated to receive solution A (Group A), 6 solution B (Group B). There were no significant differences between the groups in age, sex, causation of diarrhea or severity of dehydration before receiving ORS. Both groups showed a satisfactory response to 24 hours of treatment with either ORS, but a significantly lower stool output (number and global weight of stools) and higher blood glucose and bicarbonate levels were detected in group A (table II).(ABSTRACT TRUNCATED AT 250 WORDS)

Diarrhea, Infantile↗

Thyroid function after surgical treatment of nontoxic goitre. A randomized study of postoperative thyroxine administration.

Following thyroid resection for nontoxic goitre, 29 euthyroid patients were randomly allocated to no medication or to 0.2 mg levothyroxine daily (17 and 12 patients). The two groups were comparable in age, sex, extent of surgery and thyroid pathology. The patients were free from other endocrine disorders and had no other medication. Serum TSH, T4 and T3 were measured and T3-resin test performed preoperatively and 14 days and 3, 6, 12 and 18 months postoperatively. All values were within normal range. Only at the 3-month follow-up could statistically significant intergroup differences be observed, with T4 higher in the thyroxine-treated and TSH higher in the untreated group, but the outset values were thereafter regained. The T3 values in both groups were slightly reduced immediately after the operation. There was no recurrence of goitre in the 18-month observation period, and none of the findings suggested that routine thyroxine treatment is of value after resection of nontoxic goitre "in Denmark".

Adult↗

A randomized comparative trial of combined versus alternating therapy with cytostatic drugs and high-dose medroxyprogesteron acetate in advanced breast cancer.

A prospective multicenter trial was conducted in 155 consecutive patients with Stage IV breast cancer randomly allocated to receive either (1) vincristin (V) 1.2 mg/m2 (maximum dose, 2 mg), Adriamycin (A) (doxorubicin) 40 mg/m2, and cyclophosphamide (C) 500 mg/m2, all intravenously on day 1, every 4 weeks, in combination with medroxyprogesteron acetate (MPA) 600 mg orally on days 1 through 14, 500 mg intramuscularly on days 1 through 28, and twice weekly afterwards (combined chemoendocrine approach) or (2) the same combination chemotherapy (VAC) for three cycles alternating with MPA in the above-mentioned dosage during 8 weeks (alternating chemoendocrine approach). Results show an overall response rate of 73% with 26% complete responses in the combined treatment arm, whereas in the alternating arm, an overall response rate of 76% with 20% complete responses was observed. In patients with more than one metastatic site, response rate was higher in the combination treatment, and only in this arm were complete responses observed in these patients. Although the median duration of response was long in both treatment arms (combination, 19 months versus alternating, 21 months), the median overall survival in both groups was not definitely prolonged (22 versus 24 months, respectively). However, results in subsets of patients suggest that the alternating chemoendocrine approach may be better for estrogen receptor (ER)-negative patients, for patients younger than 51 years of age, and for patients with a disease-free interval of 1 year or less. Patients with these parameters probably belong to the same population. It is concluded that combination of chemotherapy and high-dose MPA may be indicated in ER-positive patients when a clinical response is urgently needed. In ER-negative patients, the alternating use of both treatment modalities deserves further investigation.

Aged↗

Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive lung disease: a clinical trial. Nocturnal Oxygen Therapy Trial Group.

At six centers, 203 patients with hypoxemic chronic obstructive lung disease were randomly allocated to either continuous oxygen (O2) therapy or 12-hour nocturnal O2 therapy and followed for at least 12 months (mean, 19.3 months). The two groups were initially well matched in terms of physiological and neuropsychological function. Compliance with each oxygen regimen was good. Overall mortality in the nocturnal O2 therapy group was 1.94 times that in the continuous O2 therapy group (P = 0.01). This trend was striking in patients with carbon dioxide retention and also present in patients with relatively poor lung function, low mean nocturnal oxygen saturation, more severe brain dysfunction, and prominent mood disturbances. Continuous O2 therapy also appeared to benefit patients with low mean pulmonary artery pressure and pulmonary vascular resistance and those with relatively well-preserved exercise capacity. We conclude that in hypoxemic chronic obstructive lung disease, continuous O2 therapy is associated with a lower mortality than is nocturnal O2 therapy. The reason for this difference is not clear.

Aged↗

A comparison of ceftazidime and tobramycin in the treatment of complicated urinary tract infections.

Sixty-two patients with complicated urinary tract infections were treated by random allocation with either ceftazidime (0.5 g every 12 h) or tobramycin (3 mg/kg/day). All patients had underlying urological conditions and a urinary tract infection with an organism sensitive to both ceftazidime and tobramycin. Thirty-two patients received tobramycin and 30 patients received ceftazidime. Thirty-two of the infections were caused by Pseudomonas spp., 16 by Escherichia coli, and the remainder by various Gram-negative organisms. Cure rates were approximately 85% in both treatment groups and side effects were minimal.

Adult↗