What blood test is available that will give an accurate estimate of radiation dose?

• A. White blood cell count
• B. Hematocrit
• C. Lymphocytes count
• D. Platelet count

Answer: (C)

Ionizing radiation hits lymphocytes the hardest among blood cells, so their numbers drop rapidly after exposure in a dose-dependent way. Measuring the lymphocyte count in a blood sample gives a practical, timely estimate of how much radiation was absorbed, which is especially useful for sorting who may need urgent care.

Other blood measures are less reliable for early dose estimation. The total white blood cell count includes many cell types with varying sensitivity, so it doesn’t map as clearly to dose. Hematocrit and platelet counts tend to change more slowly or at higher doses, making them poorer indicators for acute exposure.

So, tracking the lymphocyte count provides the most informative quick read on radiation dose in the early period after exposure.