We are currently updating our website, and will have our new version online soon. Please check back later this fall.

Mailing List

Subscribe to the KT Canada mailing list

Login

Welcome

Signup

Once you have signed up, you will receive a confirmation email with your username and password. To activate your account, follow the instructions in the email.

 

Centre for Evidence-
Based Medicine

Completed Diagnosis Worksheet for Evidence-Based Neonatal Medicine

Citation

Davis P., Turner-Gomes S., Cunningham K., et al. Precision and Accuracy of Clinical and Radiological Signs in Premature Infants at Risk of Patent Ductus Arteriosus. Arch Pediatr Adolesc Med 1995; 149: 1136-1141.

Are the results of this diagnostic study valid?

  1. Was there an independent, blind comparison with a reference ("gold") standard of diagnosis?
    Yes. Comparison to Doppler flow echocardiogram.
  2. Was the diagnostic test evaluated in an appropriate spectrum of patients (like those in whom it would be used in practice)?
    Yes. Infants had birth weights less than 1750 grams, and were between 3 and 7 days old. A third of the cohort was intubated and mechanically ventilated at the time of study.
  3. Was the reference standard applied regardless of the diagnostic test result?
    Yes

Are the valid results of this diagnostic study important?

As infants in this study were examined independently by at least three and up to five assessors, a single 2x2 table cannot be generated based on published averages. Below are the mean sensitivities, specificities, and positive predictive values. Likelihood ratios are reported for the presence of all three clinical signs (increased pulse volume, active precordium, and cardiac murmur), and for the absence of any clinical sign.

Clinical Sign Sensitivity Specificity + Likelihood Ratio
Increased pulse volume 43% 74% 1.6
Active Precordium 26% 85% 1.7
Cardiac Murmur 42% 87% 3.0

Positive Predictive Value
= 22% (pulse volume); 36% (precordium); 51% (murmur).

Pre-test Probability (prevalence) of PDA
= 23%.

Pre-test-odds = prevalence/(1-prevalence)
= 0.299

Likelihood ratio for the presence of PDA with all three clinical signs
= 3.7

Post-test odds
= Pre-test odds x Likelihood Ratio
= 1.106

Post-test Probability of PDA with all three clinical signs
= Post-test odds/(Post-test odds + 1)
= 53%

Likelihood ratio for the presence of PDA without any clinical sign
= 0.6

Post-test odds
= Pre-test odds x Likelihood Ratio
= 0.179

Post-test Probability of PDA without any clinical sign
= Post-test odds/(Post-test odds + 1)
= 15%

Can you apply this valid, important evidence about a diagnostic test in caring for your patient?

Do these results apply to your patient?

  1. Is the diagnostic test available, affordable, accurate, and precise in your setting?
    Clinical exam is readily available but its accuracy and precision are poor.
  2. Can you generate a clinically sensible estimate of your patient's pre-test probability (from practice data, from personal experience, from the report itself, or from clinical speculation)
    In the US National Collaborative Study, a PDA was detected in 20% of all infants who weighed 1750 grams or less at birth. Within the study cohort, the prevalence of PDA increased with decreasing birth weights (Pediatrics 1983; 71:364-72).
  3. Will the resulting post-test probabilities affect your management and help your patient? (Could it move you across a test-treatment threshold?; Would your patient be a willing partner in carrying it out?)
    No. The absence of any clinical signs does not rule out PDA; the presence of all three clinical signs results in a post-test probability of only 53%, too low to justify the use of therapeutic indomethacin with its potentially adverse effects.
  4. Would the consequences of the test help your patient?
    No.

Additional Notes

  1. The investigators also examined the interobserver variability in identifying the clinical signs. In general, the precision was poor (weighted kappas 0.15 to 0.41) indicating great variability in the ability of clinicians to identify the clinical signs.
  2. And what about that second paper which was retrieved from PubMed: Its authors come to the same conclusion: "Echocardiography is required for the reliable early diagnosis of a PDA in ventilated preterm infants" J Paediatr Child Health 1994; 30:406-11
  3. Continue to CAT