Sickle Cell Disease
Journal report by Buchanan and Glader entitled, "Leukocyte Counts in Children With Sickle Cell Disease" (132:396-398, 1978), concluded in part that "an absolute band count greater than 1,000/\g=m\L suggests bacterial infection in children with sickle cell anemia." They found such a level in 14 of 16 episodes of bacterial infection but in only three of 35 episodes of vaso-occlusive crisis. In an attempt to evaluate this finding, we reviewed our experience with 15 episodes of septicemia and ten of meningitis that have been reported in part in a previous communication.1 Cases were selected on the basis of age (younger than 18 years) and a positive bacterial culture of blood or CSF. In addition, we reviewed the records of 30 children hospitalized for painful crisis in whom infection was not considered a contributing factor. The first leukocyte and differential cell count obtained within 24 hours of the hospital admission was used for evaluation. Twelve of the 25 (48%) episodes of septicemia and meningitis were associated with an absolute band count greater than , /µ-L compared with one of 30 (3.3%) of those hospital¬ ized for painful crisis. Alternatively, a criteria previously suggested to indi¬ cate bacterial infection in hematologically normal children (neutrophil count >10,000^L, band count >500/ µL)2 would have fit 22 of 25 (88%) of the children with infection but would have falsely indicated an infectious process in 11 of the 30 (36.7%) with painful crisis. Our best separation occurred with an absolute neutrophil count greater than 15,000/µ or a band count greater than 500^L, which identified 20 of 25 (80%) infec¬ tions and which was found in only three of 30 (10%) children with painful crisis. In summary, we support the conclu¬ sion that a band count of 1,000^L indicates bacterial infection in chil¬ dren with sickle cell disease. However, since one half of our children with proved bacterial infection did not
Sir.\p=m-\Arecent
demonstrate this finding, we wish to emphasize that a lower count cannot be used to exclude the diagnosis. We also suggest, with the same disclaim¬ er, that an absolute neutrophil count greater than 15,000^L or a band count greater than 500^L or both indicate probable bacterial infection in children with sickle cell disease. CHARLES PEGELOW, MD DARLEEN POWARS, MD GARY D. OVERTURF, MD Division of Pediatric Hematology/Oncology and CommunicableDiseases University of Southern California School of Medicine 1129 N State St Los Angeles, CA 90033 1. Overturf GD, Powars D, Baraff LJ: Bacterial meningitis and septicemia in sickle cell disease. Am J Dis Child 131:784-787, 1977. 2. Todd JK: Childhood infections: Diagnostic value of peripheral white blood cell and differential cell counts. Am J Dis Child 127:810-816,
observed differences in scores are valid rather than the result of a psychologist's expectations of abilities in abused and nonabused children? Finally, in Fig 1 and 3, why use numerator data (number of children) on the y-axis and proportions within the bars? The subsequent percentage figures within the bars are not related to their height and thus confuse rath¬ er than clarify the relationship being described. The control of bias and a lucid presentation of data are as important as the use of an appropriate test statistic in clinical research. JOHN M. PASCOE, MD Robert Wood Johnson Clinical Scholar C. E. DAVIS, PHD Department of Biostatistics University of North Carolina at Chapel Hill Chapel Hill, NC 27514
1974.
Child Abuse
Sir.\p=m-\Itis difficult to disagree with the interest shown by Dr Goldson et al (Am J Dis Child 132:790-793, 1978) in the promotion of "good parenting skills." However, their failure to discuss bias and their confusing use of graphs result in a paper that is less than persuasive. If chance does not explain an observed association in a sample, it does not necessarily follow that the observed association is valid. There are several forms of bias that may produce an observed association in a sample that is not valid for the referent population. The article by Goldson et al demonstrates at least two forms of bias that deserve consideration. The first is selection bias. How do their 52 abused and 23 nonabused study children compare with the 140 subjects in the initial prospective study and is it reasonable to generalize from this nonrandomly selected sample of abused children to all abused children? The second is expectation bias. Why should we feel confident that the
In Reply.\p=m-\DrsPascoe and Davis have raised several issues that also concerned us in the preparation of this article. First, we were as concerned as they were regarding selection of the subjects involved in this study. It was precisely this concern that led us to include all of those subjects, and only those subjects, on whom data concerning all of the variables were available. No other criteria were used for selection. In reviewing subjects on whom all of the data were not available, the selection that we made did not seem to be biased since the incomplete data were randomly distributed with regard to the missing variables. Furthermore, had we included subjects on whom incomplete data were available, we would have been presenting an incomplete and confusing picture of the population studied. Second, the correspondents are correct in their comments concerning the possibility of expectation bias with respect to the developmental assessment. It is true that the examiners knew whether or not a particular subject had been abused or nonabused. However, since the examiners
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Journal report by Buchanan and Glader entitled, "Leukocyte Counts in Children With Sickle Cell Disease" (132:396-398, 1978), concluded in part that "an absolute band count greater than 1,000/\g=m\L suggests bacterial infection in children with sickle cell anemia." They found such a level in 14 of 16 episodes of bacterial infection but in only three of 35 episodes of vaso-occlusive crisis. In an attempt to evaluate this finding, we reviewed our experience with 15 episodes of septicemia and ten of meningitis that have been reported in part in a previous communication.1 Cases were selected on the basis of age (younger than 18 years) and a positive bacterial culture of blood or CSF. In addition, we reviewed the records of 30 children hospitalized for painful crisis in whom infection was not considered a contributing factor. The first leukocyte and differential cell count obtained within 24 hours of the hospital admission was used for evaluation. Twelve of the 25 (48%) episodes of septicemia and meningitis were associated with an absolute band count greater than , /µ-L compared with one of 30 (3.3%) of those hospital¬ ized for painful crisis. Alternatively, a criteria previously suggested to indi¬ cate bacterial infection in hematologically normal children (neutrophil count >10,000^L, band count >500/ µL)2 would have fit 22 of 25 (88%) of the children with infection but would have falsely indicated an infectious process in 11 of the 30 (36.7%) with painful crisis. Our best separation occurred with an absolute neutrophil count greater than 15,000/µ or a band count greater than 500^L, which identified 20 of 25 (80%) infec¬ tions and which was found in only three of 30 (10%) children with painful crisis. In summary, we support the conclu¬ sion that a band count of 1,000^L indicates bacterial infection in chil¬ dren with sickle cell disease. However, since one half of our children with proved bacterial infection did not
Sir.\p=m-\Arecent
demonstrate this finding, we wish to emphasize that a lower count cannot be used to exclude the diagnosis. We also suggest, with the same disclaim¬ er, that an absolute neutrophil count greater than 15,000^L or a band count greater than 500^L or both indicate probable bacterial infection in children with sickle cell disease. CHARLES PEGELOW, MD DARLEEN POWARS, MD GARY D. OVERTURF, MD Division of Pediatric Hematology/Oncology and CommunicableDiseases University of Southern California School of Medicine 1129 N State St Los Angeles, CA 90033 1. Overturf GD, Powars D, Baraff LJ: Bacterial meningitis and septicemia in sickle cell disease. Am J Dis Child 131:784-787, 1977. 2. Todd JK: Childhood infections: Diagnostic value of peripheral white blood cell and differential cell counts. Am J Dis Child 127:810-816,
observed differences in scores are valid rather than the result of a psychologist's expectations of abilities in abused and nonabused children? Finally, in Fig 1 and 3, why use numerator data (number of children) on the y-axis and proportions within the bars? The subsequent percentage figures within the bars are not related to their height and thus confuse rath¬ er than clarify the relationship being described. The control of bias and a lucid presentation of data are as important as the use of an appropriate test statistic in clinical research. JOHN M. PASCOE, MD Robert Wood Johnson Clinical Scholar C. E. DAVIS, PHD Department of Biostatistics University of North Carolina at Chapel Hill Chapel Hill, NC 27514
1974.
Child Abuse
Sir.\p=m-\Itis difficult to disagree with the interest shown by Dr Goldson et al (Am J Dis Child 132:790-793, 1978) in the promotion of "good parenting skills." However, their failure to discuss bias and their confusing use of graphs result in a paper that is less than persuasive. If chance does not explain an observed association in a sample, it does not necessarily follow that the observed association is valid. There are several forms of bias that may produce an observed association in a sample that is not valid for the referent population. The article by Goldson et al demonstrates at least two forms of bias that deserve consideration. The first is selection bias. How do their 52 abused and 23 nonabused study children compare with the 140 subjects in the initial prospective study and is it reasonable to generalize from this nonrandomly selected sample of abused children to all abused children? The second is expectation bias. Why should we feel confident that the
In Reply.\p=m-\DrsPascoe and Davis have raised several issues that also concerned us in the preparation of this article. First, we were as concerned as they were regarding selection of the subjects involved in this study. It was precisely this concern that led us to include all of those subjects, and only those subjects, on whom data concerning all of the variables were available. No other criteria were used for selection. In reviewing subjects on whom all of the data were not available, the selection that we made did not seem to be biased since the incomplete data were randomly distributed with regard to the missing variables. Furthermore, had we included subjects on whom incomplete data were available, we would have been presenting an incomplete and confusing picture of the population studied. Second, the correspondents are correct in their comments concerning the possibility of expectation bias with respect to the developmental assessment. It is true that the examiners knew whether or not a particular subject had been abused or nonabused. However, since the examiners
Downloaded From: http://archpedi.jamanetwork.com/ by a Penn State Milton S Hershey Med Ctr User on 05/23/2015
