Human placental alkaline phosphatase (hPLAP)

Human placental alkaline phosphatase (hPLAP) is an isoenzyme of alkaline phosphatase (AP) and is physiologically formed in the syncytiotrophoblasts of the placenta. It is measurable in the expectant mother’s blood from the 12th week of pregnancy.

Using monoclonal antibodies, hPLAP can be measured independently of other AP isoenzymes.

Reference ranges
Pathologically increased values are found in germ cell tumours in men (seminomas approx. 50-90 %, non-seminomas 20-35 %). In smokers, the values are up to 10 times above the reference range, making it unnecessary to determine hPLAP in smokers. For this reason, in addition to AFP, beta-HCG and LDH, hPLAP carries a certain significance for non-smokers in the prognostic assessment of germ cell tumours.

Diagnostics
A complete drop in the increased hPLAP values before surgery or medicinal therapy is regarded as a favourable prognostic factor.
In addition, an increase of one or more of the above-mentioned tumour markers can indicate a relapse earlier than imaging procedures.

HPLAP has the highest level of marker incidence! In a study (1), incidences of HCG, LDH and hPLAP were identified in 35 % (159/460 patients), 34 % (99/291) and 56 % (53/95), respectively. In another study (2), serum hPLAP values were detected in no fewer than 94 % of 361 patients. HPLAP increases the detection rate significantly.

Pre-orchiectomy incidence

NSeminoma stageCombined HCG and LDH, % hPLAP alone (HCG and LDH negative), %Combined HCG, LDH and hPLAP, %
Weisbach et al. (1) 119Not specified691584
Albrecht et al. (2)361Stage I383674
Higher671986

hPLAP optimises therapy control and monitoring

  • HPLAP has the highest sensitivity for detecting metastases following orchitectomy.
  • hPLAP is an excellent marker for detecting a relapse in cases of seminomas.
Weisbach et al. (1)HCGLDHhPLAP
Metastatic diseases N=397N=271 N=115
Sensitivity 42 % (n=137) 46 % (n=83) 51 % (n=39)
Specificity 95 % (n=260)96 % (n=188) 91 % (n=76)
Patients with a relapse N=2790 N=2033 N=611
Sensitivity 54 % (n=35) 54 % (n=26) 100 % (n=6)

In the Albrecht study (2), 77 % of patients with a relapse were identified by combining HCG, LDH and hPLAP.

Without hPLAP, 23 % of patients with a relapse would not have been identified.

Test material
At least 1 ml of serum


Literature
1. Weissbach L., Bussar-Maatz R., Mann K. The value of tumor markers in testicular seminomas. Eur Urol 1997; 32; 16-22
2. Albrecht W., Jeschke K., Stoiber F., et al. PLAP: improving the management of seminomas. Tumor Biol 2000; 21 (suppl 1): 41
3 Pottek T.S., Hartmann M., Bokemeyer C., Nachsorge und Spättoxizitäten bei Hodentumoren, Dt. Ärzteblatt; Vol.102; Iss. 48; Dec. 2005; A3342-3348
4. European consensus on diagnosis and treatment of germ cell cancer: a report of the European Germ Cell Cancer Consensus Group (EGCCCG), Annals of Oncology 15: 1377-1399, 2004

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