Serum or adipose tissue PCB levels can indicate exposure, but they are difficult to interpret clinically.
Some researchers believe that PCB levels in the serum and adipose tissues provide a reliable measurement of long-term exposure. Although PCB levels in the serum and other tissues can be measured by many laboratories, there are no standardized techniques for quantifying these compounds, and no reference values against which patient samples can be compared. Because these tests are likely to be inconclusive as well as expensive and time-consuming, analysis of either serum or adipose tissue samples is not recommended unless the exposure has been massive. In all but the most extreme cases, therefore, the diagnostic workup should be limited to liver function tests and dermatologic examination, with skin biopsy of lesions.
The American Academy of Pediatrics(AAP) does not recommend testing breast milk for PCBs, and encourages breastfeeding in all but the most unusual circumstances.
The question of measuring PCB levels most frequently arises in the context of discussions about breastfeeding. Although PCBs accumulate in breast milk, and breast-fed infants might be at additional risk because human milk contains a steroid that inhibits PCB metabolism and excretion (ATSDR 2000a), AAP has concluded that the risks posed by PCBs in breast milk are outweighed by the benefits of breastfeeding in all but the most unusual circumstances. Therefore, AAP does not recommend that breast milk be tested for PCBs. In unusual circumstances, local health department officials who are aware of the PCB problems in the region where high exposures have occurred should be consulted (AAP 1999).
Elevated hepatic enzyme levels are of limited value in diagnosing exposure to PCBs.
In the absence of chloracne, liver function tests provide the most consistent evidence of PCB toxicity; however, these tests are of questionable value because they are nonspecific. Also, normal liver enzyme values do not rule out significant exposure; body burden still might be elevated. PCB conjugates can often be detected in urine after exposure, but their analysis is expensive, unreliable, and not recommended.
What confirmatory laboratory test can be ordered to establish the diagnosis of PCB exposure?
6.
The patient requests a serum PCB analysis. The laboratory reports a level of 125 ppb, with no normal range indicated. How will you interpret this report?
