Sorted By Test Name - Mayo Medical Laboratories

9864
NEZPP
300009
been identified as surrogate markers for mutation status and can be evaluated by flow cytometric
immunophenotyping. ZAP-70 (70-kDa zeta-associated protein) is an intracellular tyrosine kinase
discovered initially because of its role in T-cell signaling. It has also been found to be associated with the
B-cell receptor in CLL. The expression of ZAP-70 (>20% of B cells) has been associated with an
increased risk for an adverse outcome in B-cell CLL and is considered an important risk factor in these
patients. ZAP-70 expression, if present, is constant throughout the patient's clinical course and thus is a
valid risk marker regardless of when it is evaluated.
Useful For: A risk factor for disease progression in patients with B-cell chronic lymphocytic leukemia
Interpretation: ZAP-70 expression is considered to be a risk factor for disease progression in patients
with B cell chronic lymphocytic leukemia (CLL). The threshold for ZAP70 staining is established by
using normal B cells as the negative cutoff value and comparing with background positive T-cell staining.
-ZAP-70-negative (20% of monoclonal B cells) CLL patients have a median time to treatment of
2.9 years. See ZAP70 Expression and Overall Survival Among Patients with B-Cell CLL in Multimedia
for survival curves.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Rassenti LZ, Huynh L, Toy TL, et al: ZAP-70 compared with
immunoglobulin heavy-chain gene mutation status as a predictor of disease progression in chronic
lymphocytic leukemia. N Engl J Med 2004 August 26;351(9):893-901 2. Crespo M, Bosch F, Villamor N,
et al: ZAP-70 expression as a surrogate for immunoglobulin-variable-region mutations in chronic
lymphocytic leukemia. N Engl J Med 2003 May 1;348(18):1764-1765 3. Orchard JA, Ibbotson RE, Davis
Z, et al: ZAP-70 expression and prognosis in chronic lymphocytic leukaemia. Lancet 2004 January
10;363(9403):105-111
Ziehl-Nielsen Stain for Acid- Fast Bacteria
Useful For: For acid-fast inclusion bodies
Reference Values:
The laboratory will provide a pathology consultation and stained slide.
Zinc Protoporphyrin, Blood
Clinical Information: The porphyrins are intermediaries in the heme synthesis pathway. When iron
is not available for heme synthesis (eg, iron deficiency), zinc protoporphyrin (ZPP) accumulates within
RBCs. Lead inhibits several enzymes in the heme synthesis pathway and causes increased levels of RBC
ZPP. ZPP is a biological marker of lead toxicity and was previously used, in conjunction with blood lead
assays, to screen for lead poisoning in children. However, because of poor sensitivity and specificity, ZPP
is no longer recommended for lead screening in children. However, ZPP remains a useful tool for
monitoring treatment of individuals with confirmed elevated lead levels.
Useful For: Evaluating iron deficiency Monitoring treatment and environmental intervention of
chronic lead poisoning
Interpretation: An elevated zinc protoporphyrin (ZPP) indicates impairment of the heme biosynthetic
pathway. In children, a blood lead level of >20 ug/dL and an ZPP level of >70 mcmol ZPP/mol heme are
indicative of lead toxicity.(1) Elevated ZPP levels in adults may indicate long-term (chronic) lead
exposure or may be indicative of iron deficiency anemia or anemia of chronic disease.
Reference Values: