Berg 2008
| Methods | Purpose: to test hypotheses that mailed advice to receive an influenza vaccine or to call a telephonic nurse service would reduce condition related inpatient bed days and emergency department visit Design: RCT Duration of study: 5 months Interval between intervention and when outcome was measured: not stated Power computation: no information provided Statistics: unit of study is household, not individual. Clustered analyses were done, including for differences in vaccination uptake using Chi2 statistics generated by the 'proc genmod' command using the 'repeated' option in SAS to account for the clustering effect on variance Data are presented such that the reader can do a comparison of the influenza vaccination uptake between groups as a secondary analysis but the trial was not explicitly designed to test if the interventions would make a difference to influenza vaccination uptake | |
| Participants | Country: USA Setting: subscribers (households) and their dependents over the age of 65 years enrolled in the Blue Cross & Blue Shield Government‐wide Service Benefit Plan in the states of Oklahoma, Rhode Island, Kentucky, California, Arizona, Utah and Colorado in October 2002. Subscribers were current or retired federal employees Eligible participants: (health status): no data provided on health status; however the 'participants' are actually 'households' Age: 65 years or older Gender: 60% female | |
| Interventions | Intervention 1: postal cue encouraging influenza vaccination (N = 26,474 people) Intervention 2: postal cue to call a nurse advice service if symptoms consistent with influenza‐like illness developed (26,846 people) Control: no postal cues sent (81453 people) | |
| Outcomes | Outcome measured: claims made to the insurance providers for inpatient bed days, emergency department visits, physician evaluation and management visits and other outpatient visits for selected respiratory or congestive heart failure ICD‐9‐CM code diagnoses claims. Physician evaluation and management visits were examined using clinical procedural terminology codes However, although not a primary outcome planned for this study, data were obtained for influenza vaccination uptake which are presented in Tables 2 and 3 in the form of rates calculated as (number of events/N in sample) x 10,000 |
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| Notes | Funding: Blue Cross Blue Shield Association, McKesson Corporation | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | "Households in all states had an equal probability of assignment into the intervention group." "The simple randomisation code was developed by using a computer random number generator between the values of 0 and 1 so that the control group was 3 times as large as the intervention group." |
| Allocation concealment (selection bias) | Unclear risk | No statement |
| Blinding (performance bias and detection bias) All outcomes | Low risk | No statement; outcome data based on billing claims |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | Attrition of participants not addressed. "Because the mailings were sent out in bulk, no information was available on undeliverable pieces." Incomplete data points for participants? Cannot assess. "Influenza vaccinations often are given in settings that do not generate claims, thus limiting the reliability of evidence of influenza vaccinations as seen via administrative claims." Analysis of whether differential attrition could affect outcomes? Not performed The study was not designed to evaluate uptake of influenza vaccination as a primary outcome, and because it is possible that participants might have received influenza vaccination from a source that did not result in a claim being made to the insurers from which the outcomes were ascertained, there is likely underestimation of the influenza vaccination uptake for all 3 study groups. However, one might argue that one would not necessarily a priori expect to see systematic difference in utilisation of uncaptured sources of influenza vaccination between these groups unless there was differential drop‐out between the groups over time. No information was presented on persons who might have dropped out because of death during the study or on persons who might have lost their insurance benefits during the study period. This is a threat to the validity of both the cardinal outcomes and the analysis of secondary outcomes we performed |
| Selective reporting (reporting bias) | Low risk | No selective reporting |