Differential Diagnosis for Laboratory Scenarios

The following differential diagnosis is organized into categories to provide a comprehensive approach to each scenario.

• Single most likely diagnosis

  • A thick orange specimen is received in the laboratory: B. Tablets deteriorated (likely due to improper storage or handling, causing the specimen to appear orange)
  • A laboratory that formerly screened all infants with the Clinitest was accused of missing a case of galactosuria: A. “Pass through” was not observed (a common issue with Clinitest, where the color change is not observed, leading to false negatives)
  • Excessive fizzing is observed when using Clinitest tablets: B. Tablets deteriorated (deteriorated tablets can cause excessive fizzing due to improper chemical composition)
  • A vegetarian consistently has false positive readings for blood on routine specimens: E. Vegetable peroxidase (certain vegetables contain peroxidase, which can cause false positive readings for blood)
  • A test on a yellow-green specimen from a jaundiced patient is negative for bilirubin: D. Bilirubin oxidized to biliverdin (bilirubin can oxidize to biliverdin, which may not be detected by the test, leading to false negatives)

• Other Likely diagnoses

  • A thick orange specimen is received in the laboratory: C. Vegetarian diet or UTI therapy (certain foods or medications can cause changes in urine color)
  • A laboratory that formerly screened all infants with the Clinitest was accused of missing a case of galactosuria: B. Tablets deteriorated (deteriorated tablets can lead to inaccurate results)
  • Excessive fizzing is observed when using Clinitest tablets: C. Vegetarian diet or UTI therapy (certain substances can cause excessive fizzing)
  • A vegetarian consistently has false positive readings for blood on routine specimens: C. Vegetarian diet or UTI therapy (other substances in the vegetarian diet or UTI therapy can cause false positives)
  • A test on a yellow-green specimen from a jaundiced patient is negative for bilirubin: E. Vegetable peroxidase (although less likely, vegetable peroxidase can interfere with bilirubin tests)

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • A laboratory that formerly screened all infants with the Clinitest was accused of missing a case of galactosuria: D. Bilirubin oxidized to biliverdin (although less likely, missing a case of galactosuria can have severe consequences, and bilirubin oxidation can be a factor)
  • A test on a yellow-green specimen from a jaundiced patient is negative for bilirubin: A. “Pass through” was not observed (missing a case of bilirubin can have severe consequences, and "pass through" not being observed can be a critical factor)

• Rare diagnoses

  • A thick orange specimen is received in the laboratory: E. Vegetable peroxidase (less likely, but possible if the specimen contains certain vegetables)
  • A laboratory that formerly screened all infants with the Clinitest was accused of missing a case of galactosuria: E. Vegetable peroxidase (less likely, but possible if the infant's diet contains certain vegetables)
  • Excessive fizzing is observed when using Clinitest tablets: D. Bilirubin oxidized to biliverdin (less likely, but possible if the tablets are exposed to certain substances)
  • A vegetarian consistently has false positive readings for blood on routine specimens: D. Bilirubin oxidized to biliverdin (less likely, but possible if the vegetarian diet contains certain substances that interfere with the test)
  • A test on a yellow-green specimen from a jaundiced patient is negative for bilirubin: B. Tablets deteriorated (less likely, but possible if the tablets are old or improperly stored)