The predictive values of a positive low-back X-ray examination in estimating future low-back pain is 336 / 424 (79 percent). In other words, in a population in which 60 percent are already at risk for future low-back pain, a positive low-back X-ray exam may raise to 79 percent the lifetime risk of such pain. If only those applicants wiht a negative examination are employed, 576 will get jobs, but 424 will be refused employment. Of the 424 refused employment because of a positive examination, 88 (21 percent) will never have low-back pain. Furthermore, of the 576 accepted for employment, 264 (46 percent) will have low-back pain.

Only half of the persons who report symptoms of low-back pain will miss any work because of it. Table 5 represents this fact

in the same 1,000 potential workers.

(Of course, those who will

never lose time from work because of low-back pain include those who will not have low-back pain during their lifetime.)

Among the 30 percent of employees with low-back pain severe enough to cause them to miss time form work a conservative estimate of the number of persons with severe low-back pain requiring disc surgery is 5 percent, giving an overall surgical rate of 1.5 percent.

At this rate of surgery, the predictive value of a positive examination is 8.4 / 424 (2 percent); in other words, 416 (98 percent) of the 424 persons refused employment would never require back surgery.

An Evaluation of the Railroads' Policy

If low-back X-ray examinations misclassify such a high percentage of job applicants as being at increased risk for future low-back pain or injury, why does the railroad industry persist in using them? Apparently, from the industry's vantage point only direct financial considerations must be taken into account because of the large number of high quality job applicants. Therefore, the industry may perceive that the cost of this relatively poor test, of low predictive value, is the only relevant cost and is still more than offset by the reduction in lost work days and costly claims.

Of particular concern to the railroad industry is the cost of low-back pain cases requiring disc surgery, because these workers usually are thirty to fifty years old, and they may develop longterm disability. At the 1.5 percent overall surgical rate (Table 3), if screening could reduce the rate of disc surgery from 15 per 1,000 to 11.5 per 1,000 (6.6/576), this might "save" 3.5 disc surgery cases per 1,000 employees. In order to find 1,000 "better risk" employees, the railroad would have to screen 1,736 applicants. At fifty dollars per examination, the cost of the Xray program for these applicants would be about $87,000.

Claims

for low-back injury cases

requiring

disc

railroads about $33,000 per case in 1971.

surgery cost the Therefore, reducing

disc surgery cases by 3.5 per 1,000 employees could save the

industry $115,000.)

This type of accounting process is indeed being used by the industry. For example, one railroad, Southern Railway System, processed 5,800 applicants in one year. Ninety percent received low-back X-ray exams for a total cost of $235,000. The medical director concluded that the cost of the whole X-ray program could be covered by saving six disc cases from employment.

Unfortunately, this narrow accounting considers only direct costs and benefits to industry and ignores potential negative social consequences. For example, it ignores the employment opportunities lost by applicants who are rejected for railroad jobs on the basis of X-ray findings and who may have trouble getting jobs elsewhere if "word gets out" about those findings. In addition, applicants who "pass" their X-ray examinations and who

are hired by the railroad may be/lulled into a false sense of security concerning future back problems. Next, there is the potential health hazard to applicants and to fetuses exposed to radiation during the examination. Finally, there is the cost of administering the examinations, which, from society's viewpoint, might better be spent in other ways, such as in supporting rehabilitation programs to help injured workers return to the work force.

SUMMARY

Low-back X-ray examinations are used widely in the railroad industry to screen applicants for employment. Through such examinations, the railroads seek (1) to decrease the number of claims for work-related low-back injuries, (2) to cut down on lost work time attributable to low-back pain or injury, and (3) to protect particularly susceptible workers from job-related hazards. Although low-back X-ray examinations have low value in estimating future low-back pain or injury, the railroad industry apparently considers this screening program to be cost-effective. However, the industry ignores such social costs as the potential radiation hazard of the examinations and the denial of employment to persons who are misclassified as being at increased risk for low-back pain or injury. On balance, the railroads seem to have embarked upon a screening program that has a significantly negative social value. Asymptomatic persons who are refused employment on this basis may have legal recourse under recently enacted federal and state statutes that prohibit employment discrimination based on an actual or a perceived handicap.