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Tracy HillNovember 6, 2011NU 517- Rapid Critical Appraisal Case-Control StudyAre the results of the study valid?How were the cases obtained?According to the authors, the case-control study was performed in Auckland, New Zealand during the 1995-1997 pertussis epidemics. A control group consisted of “98 infants admitted to the hospital with a coughing illness who were culture negative for Bordetella pertussis and had no B pertussis DNA detected in their nasopharyngeal sample after amplification by polymerase chain reaction” (p.852). Pertussis was defined as “cough lasting at least two weeks with coughing paroxysms, inspiratory ‘whoop’ or vomiting after coughing.Were appropriate controls selected? YesAdequate case comparison was completed to ensure results and in an attempt to eliminate potential bias. Grant et al (2003) identified 179 subjects enrolled in the study with a diagnosis of pertussis on discharge from the hospital, and according to the authors, did not differ from the non-enrolled subjects in “age, sex, ethnicity, gestation, birth weight, or social deprivation score (p. 853). The authors reported that the “controls and the other two groups did not differ in age, proportion of infants of non-European ethnicity or social deprivation index” (p. 853), when comparing the control group to those groups who had not been approached for enrollment in the study, and those for whom informed consent was not obtained. It was found, however, when infants with pertussis were compared to those without pertussis, that the infants with pertussis were younger, had mothers with only primary school education, lived in more crowed households, and lived in the socially “deprived fifth” (p. 853). The authors did not find a statistical difference, however, between the two groups of infant’s characteristics, mother’s characteristics, or household characteristics. Fineout-Overhold and Johnston (2011) report that case-control studies “with historical controls are generally viewed as lower on the hierarchy of evidence than those studies with concurrent controls, because there is more likelihood for bias” (p.105). As a result, an important consideration is that the authors did interview each infant’s care giver and reviewed the participant’s health record book or the family doctor’s records to confirm immunizations of the infants, and that could potentially indicate a small potential bias.Were data collection methods the same for the cases and controls?YesThe same method of collecting data was used for both the case and control groups. Nasopharyngeal samples for culture and for polymerase chain reaction were obtained from 98% and 86% of the sample, respectively. What are the results?Is an estimate of effect given (do the numbers add up)?YesAre there multiple comparisons of data?YesConsidering this is only a brief report, and data is limited, the authors did include a table showing the ‘Odds ratio (CI 95%) of catching pertussis’ and its association ‘with delays in giving pertussis vaccine’, and in the article the authors describe using multivariate analysis to describe the associated risk of delayed immunization series with an increased risk of being hospitalized (odds ratio 4.50). Is there any possibility of bias or confounding?NoAs previously stated, the authors did interview each infant’s care giver and reviewed the participant’s health record book or the family doctor’s records to confirm immunizations of the infants, and that could potentially indicate a small potential bias. However, multiple means of comparison were utilized to eliminate potential bias. The measure of social deprivation was done by using the New Zealand social deprivation index. Care was also taken to ensure consideration of confounding variables. The authors noted the enrolled study participants did not show statistical difference from the non-enrolled infants in age, sex, ethnicity, gestation, birth weight, or social deprivation. The study question “Does a delay in infant pertussis immunization increase chances of pertussis related hospitalization?” also fits the study design.Will the results help me in caring for my patients?YesThe information shown in this study further solidifies my belief that children, adolescents and adults be immunized against pertussis and other vaccine-preventable diseases as recommended by the Centers for Disease Control (CDC) (vaccines, 2011).Were the study patients similar to my own?Yes, they could be, considering I plan to see infants and children, as well as adults, as part of my future Family Nurse Practitioner role. In my current practicum setting, we see patients of all ages, from newborn to elderly, and there are several parents of patients who have not had their children immunized with the pertussis vaccine, so this study is pertinent to my practice. How do the results compare with previous studies?Although the authors do not provide a review of the literature in this brief report, a meta-analysis and support from the American Academy of Pediatrics and the American Academy of Family Physicians, it is recommended to receive the pertussis immunization series at 2 months, 4 months, 6 months, 15 through 18 months, and then at 4-6 years of age (Drutz, 2011). According to Drutz (2011) the efficacy of three or four doses of DTaP was 59% to 89% effective in preventing moderate to severe pertussis disease. The effectiveness of vaccination is demonstrated by decline in the disease in the U.S. since the 1940s.What are my patients/family’s values and expectations for the outcome?The expectations of patients and family members, in accordance with the results of the study, may be that there would be less incidence of the disease or that the severity of illness would be decreased after proper and timely immunization. Immunization with Tdap is particularly recommended for adults and adolescents who will have, or anticipate having, close contact with an infant aged less than 12 months, since they are not fully vaccinated and are more at risk of contracting the disease. All healthcare workers, especially those who have contact with children, should receive Tdap as well (Drutz, 2011). I believe most of my patients would agree that through immunization with Tdap there would be a decreased incidence of pertussis related illness or a decreased severity of illness after immunization. ReferencesDrutz, J. E. (2011, May). Diphtheria, tetanus and pertussis immunization in infants and children0 through 6 years of age. Retrieved from UpToDate database.Grant, C., Roberts, M., Scragg, R., Stewart, J., Lennon, D., Kivell, D., & ... Menzies, R. (2003).Delayed immunisation and risk of pertussis in infants: unmatched case-control study.BMJ: British Medical Journal (International Edition), 326(7394), 852-853. O'Mathuna, D. P., Fineout-Overholt, E., & Johnston, L. (2011). Critically appraising quantitativeevidence for clinical decision making. In B. M. Melnyk & E. Fineout-Overholt,Evidence-based practice in nursing & healthcare: A guide to best practice (2nd ed., pp.104-107). Philadelphia, PA: Wolters Kluwer: Lippincott Williams & Wilkins. ................
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