From the Research
The minimum volume of serum required for parathyroid hormone (PTH) testing in neonates is typically 0.2 to 0.5 mL (200-500 microliters). This small volume is sufficient for most modern laboratory analyzers that use immunoassay techniques for PTH measurement 1. When collecting blood for PTH testing in neonates, it's essential to use appropriate microcollection techniques and containers, such as microtainer tubes with serum separator. The sample should be handled carefully to avoid hemolysis, which can interfere with accurate results. Blood should be allowed to clot completely before centrifugation, and the serum should be separated promptly. If testing cannot be performed immediately, the serum should be refrigerated at 2-8°C for up to 8 hours or frozen at -20°C for longer storage.
Some key points to consider when collecting and handling blood samples for PTH testing in neonates include:
- Using microcollection techniques and containers to minimize blood volume
- Avoiding hemolysis to ensure accurate results
- Allowing blood to clot completely before centrifugation
- Separating serum promptly
- Refrigerating or freezing serum if testing cannot be performed immediately
The small volume requirement reflects technological advances in laboratory medicine that allow for accurate hormone measurements using minimal blood volumes, which is particularly important in neonates where blood conservation is critical to prevent iatrogenic anemia. According to the most recent study 1, the estimated range of PTH levels in very low birth weight infants without severe neonatal morbidity is 0.9-11.9 pmol/l (8.5-112.3 pg/mL), which can be measured using a small volume of serum.
In terms of the relationship between PTH levels and other laboratory markers of bone metabolism, the study found that there was no statistically significant correlation between PTH level and 25(OH)D, C3-epimers of 25(OH)D, S-Ca, S-P, or ALP during the first month of life 1. However, from the second month of life, there was a moderately significant correlation between PTH and 25(OH)D, calcium/creatinine ratio, and phosphorus/creatinine ratio.
Overall, the minimum volume of serum required for PTH testing in neonates is 0.2 to 0.5 mL (200-500 microliters), and careful collection and handling of blood samples are essential to ensure accurate results.