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Centre for Evidence-
Based Medicine

Completed Therapy Worksheet for Evidence-Based Nursing


Macknin ML, Piedmonte M, Calendine C, Janosky J, Wald, E. Zinc gluconate lozenges for treating the common cold in children. A randomized controlled trial. JAMA 1998;279:1962-7

Are the results of this single preventive or therapeutic trial valid?

  1. Was the assignment of patients to treatments randomised?
    And was the randomisation list concealed?
    Yes. Computer generated randomisation code given to pharmacist who prepared medication packages.
  2. Were all patients who entered the trial accounted for at its conclusion? -and were they analysed in the groups to which they were randomised?
    Yes, all children were accounted for. 117/124 children (94%) allocated to the intervention completed the trial and 122/125 children (98%) allocated to placebo completed the trial. Authors stated that analyses were conducted using intention-to-treat principles.
  3. Were patients and clinicians kept "blind" to which treatment was being received?
    Yes, both study personnel and participants were blinded to allocation. Medication packages were identical in appearance except for the identifying code.
  4. Aside from the experimental treatment, were the groups treated equally?
  5. Were the groups similar at the start of the trial?
    At baseline, groups were similar for age; sex; race; body surface area; allergies; smoking; smoking in the home; history of colds, infections, and complications; and temperature. 25% of the intervention group took vitamin supplements compared with 16% of the placebo group (p=0.08). Students were asked to stop taking zinc-containing vitamins or mineral supplements during the study. 7.5% of the intervention group had a history of asthma compared with 14% of the placebo group (p=0.10); analysis showed that this imbalance had no effect on outcome.

Are the valid results of this randomised trial important?

Main outcome was time to resolution of cold symptoms. Secondary outcomes included school absences and adverse effects.

Median time to resolution of cold symptoms did not differ between groups (9 days for both groups). {Because time to resolution of cold symptoms is a continuous variable, RRR, ARR, NNT cannot be calculated.}

School absences (number of children with absences) Relative Risk Reduction
Absolute Risk Reduction
Number Needed to Treat
Zinc lozenges
20.8% 18.5% (20.8%-18.5%)/20.8%
= 11.1%

95% CI -46.7 to 45.9
20.8% - 18.5%
= 2.3%
= 44 pts

95% CI 8 to infinity
Adverse effects (e.g., bad taste reactions; nausea; mouth, tongue or throat irritation; and diarrhoea) Relative Risk Increase
Absolute Risk Increase
Number Needed to Harm
Zinc lozenges
79.8% 98.6% (79.8%-88.6%)/79.8% =

95% CI -21.7 to 3.7
79.8% - 88.6%
= 8.8%
= 11 pts

95% CI 6 to infinity

Can you apply this valid, important evidence about a treatment in caring for your patient?

Do these results apply to your patient?

  1. Is your patient so different from those in the trial that its results can't help you?
    Similar - Grades 1 to 12 students in 2 suburban school districts in Cleveland, Ohio, USA.

How great would the potential benefit of therapy actually be for your individual patient?

  1. Method I: f
    Risk of the outcome (school absence) in your patient, relative to patients in the trial. expressed as a decimal: 1

    NNT/f = 44/1 = 44 (95%CI 8 to infinity)
    (NNT for patients like yours)
  2. Method II: 1 / (PEER x RRR)
    Your patient's expected event rate if they received the control treatment: PEER:______

    1 / (PEER x RRR) = 1/________ = _______
    (NNT for patients like yours)

Are your patient's values and preferences satisfied by the regimen and its consequences?

  1. Do your patient and you have a clear assessment of their values and preferences?
    Patient values/preferences unknown but these could be discussed with the child and parent; however, I would want a treatment that does more good than harm.
  2. Are they met by this regimen and its consequences?
    No (based on my values/preferences) - no apparent benefit in terms of symptom relief and school absences, and potential for adverse effects.

Additional Notes

Interestingly, the article that you identified from your search of Best Evidence that evaluated the effectiveness of zinc lozenges in adults with cold symptoms found that zinc lozenges WERE effective. (see Mossad SB, Macknin ML, Medendorp SV, Mason P. Zinc gluconate lozenges for treating the common cold. A randomized, double-blind, placebo-controlled study. Ann Intern Med. 1996;125:81-8 ).

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