In the medical and laboratory setting, the integrity of specimens is crucial for accurate test results. Some specimens are highly sensitive to light and can undergo chemical changes when exposed to light, leading to inaccurate or invalid test outcomes. Here are some types of specimens that must be protected from light:

1. Vitamin B12

• Reason: Vitamin B12 levels in blood samples are highly sensitive to light. Exposure to light can lead to degradation of the vitamin, causing inaccurate results in tests related to vitamin B12 deficiency.

2. Bilirubin

• Reason: Bilirubin, a product of red blood cell breakdown, is commonly tested in newborns to assess jaundice. This specimen is extremely sensitive to light, and exposure can lead to the breakdown of bilirubin, resulting in falsely low readings.

3. Folate

• Reason: Folate (also known as vitamin B9) is another important nutrient whose levels are measured in blood samples. Like Vitamin B12, folate levels can degrade when exposed to light, potentially leading to inaccurate test results.

4. Porphyrins

• Reason: Porphyrins, which are chemicals involved in the production of hemoglobin, are sensitive to light. If these specimens are exposed to light, they can decompose, affecting the accuracy of the test results.

5. Some Medications in Blood Specimens

• Reason: Certain medications, such as phenytoin, methotrexate, and digoxin, can be unstable when exposed to light, which can affect their concentration and lead to erroneous results when measured in a lab.

How Are Light-Sensitive Specimens Handled?

To protect these specimens from light, laboratory staff use a variety of techniques:

• Amber-colored containers: Specimens are often placed in amber vials or tubes that filter out harmful light wavelengths.
• Light-tight bags: Specimens may be wrapped in aluminum foil or placed in light-proof bags to block exposure.
• Storage in dark environments: Specimens are sometimes stored in dark, cool places until they can be processed.

Conclusion

Proper handling and storage of specimens that are sensitive to light are essential to ensure accurate test results. Always follow specific guidelines for each type of specimen to prevent exposure to light, which could alter their chemical composition and lead to misleading test outcomes.