Comparative study of total prostate specific antigen and free to total prostate specific antigen ratio in the diagnosis of prostate cancer

Mymensingh Med J. 2012 Jan;21(1):98-102.

Abstract

This descriptive study was done to compare total Prostate Specific Antigen (tPSA) and the Free to Total Prostate Specific Antigen [(F/T) PSA] ratio measurements for prostate cancer detection. This study included a total of 43 patients with suspected prostate cancer observed over a period of 12 months. Out of 43 consecutive male patients (mean age 69±9.39 years, range 48-100 years), 32 had benign disease (74%) and 11 had prostate carcinoma patients (26%), who had histologically proven prostate cancer. The mean total PSA was 67.9 ng/ml and 12.4 ng/ml in patients with carcinoma prostate and nodular hyperplasia of prostate (NHP) respectively (p<0.05). The mean free PSA in carcinoma patients was 7.4±9.8 ng/ml and in NHP patients it was 2.3±4.1 ng/ml. The difference in mean free PSA concentration was significant (p<0.05). The free to total PSA ratio in two groups was significantly different (p<0.01) from each other. In carcinoma patients, mean F/T PSA ratio was 0.144±0.152 as compared 0.328±0.076 in patients with benign disease. The sensitivity and specificity of the test was calculated at different F/T PSA ratio cutoff. At 0.1 cut off value, sensitivity of the test was 64% and specificity was 84%. The positive predictive value (PPV) was 58% and negative predictive value (NPV) was 87%. From cutoff value of 0.12 to 0.16, sensitivity was increased from 64% to 91% but specificity was reduced from 84% to 59%. The PPV did not show much change and NPV was increased from 89% to 95%. Increasing the cut off value thereafter showed no change in sensitivity but specificity was further reduced to 41%. Therefore in this patient, F/T PSA ratio cut off of 0.15 was found to be the appropriate cutoff value. In 43 men who were biopsied, 11(26%) prostatic carcinoma were identified. Only one patient (9.1%) had F/T PSA ratio above 0.15 and diagnosed by biopsied. Out of 32 patients who were negative for malignancy, 13 patients had F/T PSA ratio more than 0.15 and 19 patients had F/T PSA ratio less than 0.15. The validity of tPSA and F/T PSA ratio in the diagnosis of prostate cancer was identified by calculating their sensitivity, specificity, PPV and NPV. In case of F/T PSA ratio the sensitivity was 91% and in conventional tPSA the sensitivity was 82%. Specificity was low in both the cases. But in tPSA the specificity was only 13% compare to 59% in F/T PSA. Positive predictive value (PPV) for tPSA was 25% and in F/T PSA it was 44%. Negative predictive value (NPV) for t PSA was 67% and for F/T PSA was 95% which was very high. The effectiveness of F/T PSA ratio at 0.15 cut off value with corresponding tPSA>10ng/ml shows sensitivity 83% in prostate cancer and 50% in NHP patient.

Publication types

  • Comparative Study

MeSH terms

  • Adenocarcinoma / diagnosis*
  • Aged
  • Aged, 80 and over
  • Carcinoma, Transitional Cell / diagnosis
  • Cross-Sectional Studies
  • Humans
  • Male
  • Middle Aged
  • Prostate-Specific Antigen / blood*
  • Prostatic Neoplasms / diagnosis*
  • Sensitivity and Specificity

Substances

  • Prostate-Specific Antigen