Question

Cardiologists identified a new q-wave pattern on electrocardiograms that they felt would predict the incidence of cardiovascular disease (cvd) among persons aged 70 years or older who were diagnosed with post-acute covid syndrome. the cardiologists performed electrocardiograms on 500 persons with the syndrome and followed them for eight years to measure the incidence of cvd. the new q-wave pattern was observed for 170 participants and it was not observed for the remainder. over the eight years, 90 persons developed cvd: 81 of these 90 people exhibited the new q-wave pattern and the remainder did not. the presence of the pattern is considered a positive test; the absence of the pattern is considered a negative test.

(a) How many persons without CVD (persons who really did not have the disease) tested positive?
(b) How many persons without CVD tested negative?
(c) What is the sensitivity of the new Q-wave pattern?
(d) What is the specificity of the new Q-wave pattern?
(e) What is the positive predictive value of the new Q-wave pattern?
(f) What is the negative predictive value of the new Q-wave pattern?

Answer 1

In this study, 89 persons without CVD tested positive for the new Q-wave pattern, while 321 persons without CVD tested negative. The sensitivity of the new Q-wave pattern was 90%, meaning it correctly identified 90% of persons with CVD. The specificity of the new Q-wave pattern was 78%, meaning it correctly identified 78% of persons without CVD. The positive predictive value of the new Q-wave pattern was 47.6%, and the negative predictive value was 97.3%.

Step-by-step explanation:

(a) The number of persons without CVD who tested positive can be calculated by subtracting the number of persons with CVD who tested positive from the total number of persons who tested positive for the new Q-wave pattern. In this case, it would be 170 - 81 = 89 persons without CVD tested positive.

(b) The number of persons without CVD who tested negative can be calculated by subtracting the number of persons with CVD who tested negative from the total number of persons who tested negative for the new Q-wave pattern. In this case, it would be 330 - (90 - 81) = 321 persons without CVD tested negative.

(c) The sensitivity of the new Q-wave pattern can be calculated by dividing the number of persons with CVD who tested positive by the total number of persons with CVD. In this case, it would be 81/90 = 0.9 or 90%.

(d) The specificity of the new Q-wave pattern can be calculated by dividing the number of persons without CVD who tested negative by the total number of persons without CVD. In this case, it would be 321/410 = 0.78 or 78%.

(e) The positive predictive value of the new Q-wave pattern can be calculated by dividing the number of persons with CVD who tested positive by the total number of persons who tested positive for the new Q-wave pattern. In this case, it would be 81/170 = 0.476 or 47.6%.

(f) The negative predictive value of the new Q-wave pattern can be calculated by dividing the number of persons without CVD who tested negative by the total number of persons who tested negative for the new Q-wave pattern. In this case, it would be 321/330 = 0.973 or 97.3%.