Heart Disease Screening in School Children

Transcription

1 Downloaded from by on November 8, 08 Heart Disease Screening in School Children A Comparison between Clinical Screening and Heart-Sound Screening By RICHARD A. NAIMAN, M.D., AND J. GORDON BARROW, M.D. THE importance of early detection of unrecognized heart disease in school children has been adequately emphasized and various technics of screening the school-age child have been suggested and attempted.'-6 Comparisons of results have been difficult because of a lack of true prevalence rates among the populations examined.,, 7 Most recently a mass field trial of screening for heart disease, among 5,000 Chicago school children, with use of high-fidelity-taped heartsound recordings was accomplished and reported. The methods, results, and costs were reviewed by the American Heart Association Committee on Heart-Sound Recording, a subcommittee of the Committee on Community Program. The following investigations were suggested: () A comparison of heart-sound taping with clinical screening should be made. () Sensitivity and specificity studies of a large group of children with proved heart disease as subjects should be repeated. () The feasibility of using lower cost, portable equipment to minimize the high reported cost of $.00 a child screened, and $, a case discovered, should be investigated. It was further recommended that approval of this technic of screening be withheld, in terms of national application, until the above investigations are completed and evaluated. The Instrumentation Unit, Heart Disease Control Program, U. S. Public Health Service, developed and recommended portable recording and playback equipment for use in field trials of heart-sound screening. The following study was undertaken with this equipment. From the Cardiovascular Disease Control Service, Georgia Department of Public Health, Atlanta, Georgia. 708 Materials and Methods The charts of two Atlanta cardiac clinics were reviewed. Oine hundred and sixty cases with various cardiac lesions among children who might be expected to attend elementary or high school were chosen. Diagnoses, descriptions of murmurs, and the results of diagnostic procedures were recorded Ninety-six of these subjects were considered to be satisfactory for study, were recalled, and undervent a cardiac examination and phonocardiogram to document the chart data. The school and grade of each child were determined. Several individuals were discarded from the study because of recent or imminent corrective surgery; several others moved, dropped from school, or did not appear for examination. Fiftv-two school childrenl with proved cardiac disease, all with a minimum of years' clinical follow-up in a children's cardiac clinic, were selected as index subjects. Each index subject defined a different school class, attended by him, in the public schools of Atlanta and Decatur, Georgia. Permission to examine these selected classes was obtained from the school administrations, local health departments, local medical societies, and individual parents. Only the principal investigators were aware of the mechanics of selection. Each class was screened clinically by one of local, board-qualified pediatricians or internists, none of whom had special cardiology training. The screening physician was asked to record the presence or absence of a heart murmur, the suspicion or nonsuspicion of cardiovascular pathology, and the anatomy of any suspected lesion. Independently, a heart-sound recording was made by a trained technician for 0 seconds at the pulmonic area (second left intercostal space) and 0 seconds at the cardiac apex.* Accurate records were kept of actual screening time by each technic. Three cardiologists, using playback equipment de- Recordings were made on Mylar recording tape at a speed of / inches per second with an Ampex 60 tape recorder as modified by the U.S.P.H.S. Heart Disease Control Instrumentation Unit. A spring-loaded contact (vibratory) preamplifying microphone was used. (irculation, Volume XXIX, May 96

2 HEART DISEASE SCREENING 709 Downloaded from by on November 8, 08 Table Agreement among Examiners Number of cases found positive by,,, or 0 tape readers All three Two One None Findings of school physician Positive 0 9 Negative signed by the Instrumentation Unit, independently "<read" each tape. The cardiologists were asked to record the same information as the screening physicians. Each nonindex child reported as "suspicious" by any reader or screening physician was recalled for examination by a cardiologist. Any previously unknown positive finding was reported both to the child's private physician and to his parent. The index study group included 0 children with congenital heart disease consisting of ventricular septal defect, atrial septal defect, atrioventricular canal, patent ductus arteriosus (one case), pulmonic stenosis and corrected transposition of the great vessels (one case), 9 children with rheumatic valvular disease, and three children with heart disease secondary to sickle-cell anemia. The results of each screening physician and tape reader were analyzed separately and compared. The results of the tape readers were then grouped and analyzed. The children suspected of heart disease, which was not confirmed at recall, were considered false positives. Results One thousand three hundred and eighty-two children were screened. Table presents the total experience with the index group. Table shows the comparative yield of each reader and the screening physicians as well as the results of grouping the three readers. Table summarizes the results of the recall examination for all children who were not members of Comparative Yield of Each Method Congenital Rheumatic Other the index group but who were suspected of having heart disease by any physician. The screening physicians identified as suspicious of heart disease 9 of the 5 index cases. The tape readers identified 9, 6, and 8, respectively. Grouping the results of the tape readers slightly increased the percentage yield. School physicians identified 6 of 0 (80 per cent) congenital heart disease subjects but only of 9 (8 per cent) of the rheumatic heart disease subjects. Tape readers demonstrated similar percentages as individuals and slightly better as a group. Of those children returning for recall examination, the screening physicians identified as suspicious 9 nonindex children of which four (0 per cent) had cardiac pathology; tape readers identified 80 nonindex children, six (7.5 per cent) of which had heart disease. Grouping of cases by loudness of murmur demonstrated that the chance of discovery of a suspect is highly correlated with the loudness of the murmur (table ) with no appreciable difference between physician and tape reader. Table 5 demonstrates that the chance of discovering a suspect is also highly related to diagnostic category (congenital or rheumatic) and that the type of diagnosis missed by physicians is the same as that missed by the readers. Similar analysis shows that diagnostic category influences the chance of discovery independent of the grade of murmur, and neither loudness of murmur nor diagnostic category alone or together discriminate between those patients likely to be discovered by a physician or a reader (e.g., both types of screening discovered of 5 cases of grade III or louder congenital heart disease but only six of rheulable Tape Screening Tape readers readers No. physician combined Circulation, Volume XXIX, May 96 6 (80%) (8%) (67%) 9 (56%) 8 (90%) 0 (%) (%) 9 (56%) (70%) 0 (%) (66%) 6 (50%) 6 8 (80%) (8%) (%) (5%) 8 (90%) (8%) (67%) (65%)

3 70 NAIMAN, BARROW Table Comparison5 of Per Cent Yield of Tape Readers vs. Screening Physicians Considering Only the Nonindex Population Screening physician Tape readers Combined Recalled and examined Recalled, did not come 6 No heart disease Probable heart (lisease 6 I'er cen-t yield 0 It should be noted that readers and agreed in suspecting only six children, three of which had heart disease. Readers and agreed in suspecting only eight children, three of which had heart disease Table Number of Index Cases Discovered by School Physicians and Tape Reader Accarding to Grade of Murmur Murmur Grade III or more II or less Physician + Pllysician + Physician- Physician N'o. cases reader + reader reader + reader Downloaded from by on November 8, 08 Table 5 Number of Index Cases Discovered by School Physicians and Tape Reader According to Diagnostic Category Diagnostic Physician -- Physician - Pisysician Physician --- category ino. cases reader + reader-- reader + reader-- Congenital 0 5 Rheumatic Other Table 6 Sensitivity and Specificity of Screening Suspected by physician Not suspected a+b (60) a Sensitivity al ~-b =- 60 -~0.55 Specificity +-d Confirmed heart disease a () b (7 ) J Confirmed no heart disease c (5) d (87) c+d () a+c (68) b±d () a+b+c+d (8) Circulaison, Volume XXIX, May 96

4 Downloaded from by on November 8, 08 HEART DISEASE SCREENING matic lesions within the same category of murmurs). By definition, sensitivity is the chance against missing a true case and specificity is the chance against falsely labeling healthy persons as a case. Grouped reader sensitivity is 0.6; physician sensitivity is Grouped reader specificity is 0.9 and screening physician specificity is The calculations are shown in table 6. The authors, using recently published prevalence figures for types of heart disease in school children in Nashville, Tennessee, calculated an expected yield of each method of screening by considering the expected prevalence of congenital and rheumatic heart disease in schools and the demonstrated sensitivity of each method. We may expect to discover 80 per cent of congenital, but only 8 per cent of rheumatic heart disease. Considering the 5: incidence of rheumatic to congenital heart disease, a school physician can be expected to discover 5 per cent of heart disease in school children; an individual tape reader may discover per cent, and three tape readers combined may be expected to discover only 55 per cent of the heart disease present in school children. If, as others report, there is an equal prevalence of congenital and rheumatic heart disease," 7 8 the expected yield becomes 58 per cent of school children with heart disease. Time-cost relationships are shown in table 7. Clinical screening costs $0.5 per child; taping costs $0.8 per child screened by one reader and $0.8 per child screened by three readers. Discussion and Conclusions Numerous prevalence studies of heart disease in children have been reported. The authors accept those of Quinn and Campbell, who report a 5: ratio of rheumatic to congenital heart disease in Nashville, Tennessee, school children, as being most consistent with experience in the State of Georgia. Studies from Chicago and Colorado report nearly identical prevalences for these two entities." 7 8 Either postulate calculates a poor expected yield of heart disease from either screening technic. All published studies agree that mitral Circulato?on, Volune XXIX, May 96 Table 7 Comparative Time/Cost Figures Number Clinical screening 8 Taping 8 Reading (each) 8 7 Children Minutes Min. / child /5-hr.day Clinical screening cost Physician $60/day screen~ is children =.9 / child Tape screening cost Technician time 0 hours $05.00 Equipment and tape ( $500 cost--year life) One cardiologist (6 hr. X $5.00) 0.00 $58.00 = 8q5/child Two additional cardiologissts $ = 80t/child These figures do not include the use of a school nurse or administrative costs, which would be the same with both methods. insufficiency is the most common cardiac lesion in childhood, representing as much as 50 per cent of all lesions. Both school physicians and tape readers were inept at identifying this lesion (7 to 5 per cent) and they also did poorly with aortic insufficiency and mitral stenosis. Such observations explain the low sensitivity of these screening technics. It is unfortunate that so few subjects with patent ductus arteriosus and atrial septal defect were included in this study. An unoperated patent ductus is a rarity in the school-age group, however, and several children with atrial septal defects were lost to the study because of corrective surgery. The authors accept the facts that recording circumstances and recordings in some classes were much less than ideal. Since two screening methods were being tested for practicality, it seemed best to accept the situations and results as they were encountered from school to school. The school physician, of course, suffered many of the same handicaps with the exception of equipment and power failure. Additional readers add only 0 per cent to the yield of tape screening and triple the cost. The advantage of cardiology training appears

5 Downloaded from by on November 8, 08 7 to be lost when the cardiologist becomes the slave to the technician's microphone placement and patient positioning as well as when he is denied the powers of his nonauditory senses. It is interesting to note that while the readers were in very good agreement on the subjects with heart disease (table ), they overlapped only slightly on false positives (table ). There is virtually no difference between the two methods in terms of sensitivity and specificity. Another facet of tape screening was that of equipment failures (four occurrences), which added to the over-all time and cost of this method. All three readers mentioned the phenomena of severe listener fatigue and soporific effect of heart sounds through earphones. It is our distinct impression that the cardiologist attrition rate would rapidly exhaust the supply of cardiologists in any large program. In conclusion, we find portable tape-screening technics with trained cardiologist readers, when compared with clinical screening by generally available community physicians, to be equally inefficient in detecting heart disease in a group of school children and two to three times as expensive. Summary Fifty-two children with known heart disease were chosen as index subjects among,8 school children. All,8 children were screened by two methods; namely, a clinical screening examination and a heart-sound tape recording with use of three independent cardiologists to read each tape. Both methods yielded nearly identical results, identifying 6 to 8 of 0 children with congenital heart disease and 0 to of 9 children with rheumatic heart disease. Using published prevalence figures for congenital and rheumatic heart disease, the authors calculate that these methods will identify NAIMAN, BARROW only to 58 per cent of heart disease existing in school-age children. There is no appreciable difference in the sensitivity or specificity of the two methods. Tape recording of heart sounds with highquality portable equipment is found to be more cumbersome, expensive, and time consuming, and of no greater sensitivity than clinical screening by available community physicians. Acknowledgment The authors wish to express their gratitude to Dr. John Cassel, Professor of Epidemiology, School of Public Health, University of North Carolina, for his help in reviewing this manuscript and his excellent suggestions for statistical analysis. References. MILLER, R. A., SMITH, J., STAMLER, J., HAHNE- MAN, B., PAUL, M. H., ABRAMS, I., GERSHON, H., EDELMAN, J., WVILLARD, J., AND STEVENS, W.: The detection of heart disease in children. Results of a mass field trial with use of tape recorded heart sounds. Circulation 5: 85, 96.. QUINN, R. W., AND CAMPBELL, E. S.: Heart disease in children. A survey of school children in Nashville, Tenn. Yale J. Biol. & Med. : 70, 96.. DEBOER, L.: Application of screening method for the detection of heart disease in children. J. School Health :, 96.. MORTON, WV., BEAVER, M. E. N., AND ARNOLD, R. C.: Heart disease screening in elementary school children. J.A.M.A. 69: 6, MORTON, W., HOFFMAN, MN., CLEERE, R. L., AND DODGE, H. J.: Comparison of three methods of screening for pediatric heart disease. J.A.M.A. 69: 69, MATTISON, B. F., LAMBERT, E. C., AND MOSHER, W. E.: Cardiac screening in a school health program. New York J. Med. 5: 966, MORTON, NV.: Heart disease prevalence in school children in two Colorado communities. Am. J. Pub. Health 5: 99, DODGE, H. J., MARESH, G. j., AND MORRIs, N. M.: Prevalence of heart disease in relation to some population characteristics of Colorado school children. Am. J. Pub. Health 8: 6, 958. Circulation, Volune XXIXiMay 96