Home landline telephone coverage and potential bias in epidemiological surveys.
OBJECTIVE
To estimate landline telephone coverage effects on potential information bias in epidemiological surveys.


METHODS
Databases of the Pesquisa Nacional por Amostra de Domicílios (National Household Sample Survey), from 1998 to 2003, were used to estimate landline telephone coverage rates in the five Brazilian geographic regions. Multiple regression analysis was used to identify factors associated with owning a landline telephone. Bias impact on 95% confidence intervals was assessed, according to the accuracy achieved in each situation.


RESULTS
In the Southern and Central-west metropolitan regions, with 70% coverage or more, associated bias was considered insignificant. In the remaining regions, related bias was above the acceptable limit (0.4), indicating possible errors in inferences drawn with a 95% confidence interval. Likelihood of access to a home landline telephone was greater among the white population with higher level of education.


CONCLUSIONS
Findings reveal that the use of residential telephone records is indicated to conduct epidemiological surveys in Brazilian states where coverage is above 70% exclusively. Specific methodologies to treat estimates obtained in regions with lower rates need to be analyzed and published.
Bernal
Regina
R
Programa de Pós-Graduação em Saúde Pública, Faculdade de Saúde Pública, Universidade de São Paulo, São Paulo, SP, Brasil. rbernal@usp.br
Silva
Nilza Nunes da
NN
D000293:Adolescent; D000328:Adult; D015982:Bias; D001938:Brazil / Q000453:epidemiology; D002908:Chronic Disease / Q000453:epidemiology*; D016001:Confidence Intervals; D004522:Educational Status; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D013689:Telephone; D044465:White People; D055815:Young Adult