What do you conclude from these results with respect to the rates of pulmonary and extra-pulmonary tuberculosis among these two groups of miners?
Do you think the groups differ with respect to the proportion of total tuberculosis that is extra-pulmonary?
Recalculate the proportions of extra-pulmonary to total TB for the miners without silicosis, if there were 1 fewer case (and 1 more case) of extra-pulmonary TB in that group (ie. 2 or 4 cases instead of 3). Does this change your answer to question 2?
In what way would statistical testing help you answer these questions?
Practical exercise
Describing results
Microbial inciters of acute asthma in urban Nigerian children Gbadero DA, Johnson ABR, Aderele WI, Olaleye OD. Thorax 1995; 50:739-745.
Objective: to determine how often acute exacerbations of asthma in children are associated with acute respiratory infection, to identify the associated pathogens, and to proffer appropriate therapeutic suggestions.
Study population:
subjects were recruited from asthmatic children attending the Pediatric Asthma Clinic of the University College Hospital over a 16 month period
children were included in the study if they were previously diagnosed as having asthma, and visited the clinic with an acute exacerbation with duration of symptoms prior to visit of less than 48 hours; only 1 episode was recorded per child
Methods:
clinical features recorded included: antecedent or concomitant symptoms; household / socioeconomic factors; frequency of previous asthma exacerbations; anthropometric measurements
Discuss how to summarize the information collected (don’t focus on statistical analyses, rather think about how to summarize the information). Prepare 1 or 2 tables (without numbers, just headings for the rows and columns) to describe the information collected for the study.
Hints:
1. Consider the study objectives. What is the main question being asked?
2. Are there two groups (or subgroups) being compared (this may not be explicit).
3. What is the health outcome being investigated? What risk factors were measured?
4. What is/are the main comparisons needed to answer the study questions?
5. How can you display the results in order to show the comparisons clearly?
Practical exercise - 2
Describing results
Risk Factors for Rifampin Mono-resistant Tuberculosis R. Ridzon, C. G. Whitney, M.T. McKenna, J. P. Taylor, S.H. Ashkar, A.T. Nitta, S.M. Harvey, S. Valway, C. Woodley, R. Cooksey, I. M. Onorato; Am J Respir Crit Care Med, 157, 1998, 1881-1884
Objective: to investigate the relationship between rifampin mono-resistant tuberculosis and use of rifabutin and to identify other risk factors for rifampin mono-resistant tuberculosis among patients with and without HIV infection
Study population: multi-centre study (9 US cities)
cases (age 20+) selected from cases of tuberculosis reported to CDC's national surveillance database from 1993 to 1995 with a first M. tuberculosis isolate resistant to rifampin and without resistance to isoniazid, ethambutol, or streptomycin.
2 matched controls 20 yr of age or older were chosen per case from tuberculosis cases with isolates demonstrating susceptibility to isoniazid, rifampin, ethambutol, and, if tested, streptomycin. Controls were the two next reported patients who matched the case by city of residence (or county, if from a rural area), HIV status, age within 5 yr and start of tuberculosis treatment within 3 mo.
What is the name of this study design?
Methods: Medical records were reviewed, including tuberculosis clinic records, hospital records, private provider records, and HIV clinic records (when applicable). Information collected included demographics (age, sex, race, birth place), history of homelessness, incarceration, HIV status, prior tuberculosis, diarrhea, and medications taken at the time of and prior to the current diagnosis of tuberculosis.
Sample of selected results (fabricated!)
