Serum PSA and radionuclide bone scan findings
A total of 167 men were included in the final population for analysis. The age range for the patient population was 35 - 93 years.
Table 1: Descriptive statistics for serum PSA values.
Bone Scan Result | Mean Serum PSA level (ng/ml) | Serum PSA level range (ng/ml) | Standard Deviation (ng/ml) |
+ve for skeletal metastases | 499.2 | 9.1 - 2747 | 751.77 |
-ve for skeletal metastases | 45.9 | 0.1 - 2000 | 176.90 |
Inconclusive for skeletal metastases | 63.8 | 4.3 - 184.6 | 63.96 |
Table 2: Descriptive statistics for serum PSA values and bone scan findings.
Serum PSA level (ng/ml) | No of patients bone scan -ve (%) for skeletal metastases | No of patients bone scan +ve (%) for skeletal metastases | No of patients with inconclusive bone scan (%) for skeletal metastases |
0 - 10.0 | 57 (41.6%) | 1 (4.8%) | 3 (33%) |
10.1 - 20.0 | 33 (23.1%) | 0 | 1 (11%) |
20.1 - 50.0 | 26 (19.0%) | 0 | 0 |
50.1 - 100.0 | 8 (5.8%) | 5 (23.8%) | 3 (33%) |
>100 | 13 (9.5%) | 15 (71.4%) | 2 (22%) |
Total | 137 | 21 | 9 |
Of the 21 patients found to be bone scan positive only 1 patient had a serum PSA below 10ng/ml. No patients found to be bone scan positive hada serum PSA within the normal range of 0 - 4 ng/ml.
As the sample population was not normally distributed, non-parametric two-independent samples tests were used to analyse the data. The mean serum PSA values for patients found to be bone scan positive and bone scan negative were significantly different with a p-value of 0.001.
The negative predictive value of a serum PSA below 10 ng/ml was 98.3%. The negative predictive value of a serum PSA below 20 ng/ml was 98.9%.
Figure 1. An Error Bar chart illustrating the 95% confidence interval for serum PSA level
Fig.: Figure 1. An Error Bar chart illustrating the 95% confidence interval for serum PSA level
Gleason score and radionuclide bone scan findings
A total of 120 patients had Gleason scores available for analysis.
Table 3: Descriptive statistics for Gleason score.Bone Scan Result | Mean Gleason score | Gleason score range | Standard deviation |
+ve for skeletal metastases | 8.31 | 4 - 10 | 1.49 |
-ve for skeletal metastases | 6.27 | 2 - 10 | 1.86 |
Inconclusive for metastases | 7.63 | 5 - 10 | 1.60 |
Figure 2. Error bar chart illustrating the 95% confidence interval of Gleason score with respect to bone scan result.
Fig.: Figure 2. Error bar chart illustrating the 95% confidence interval of Gleason score with respect to bone scan result.
Using a two-independent samples test, a significant difference with a p value of 0.001 was obtained between the Gleason scores of bone scan positive and bone scan negative patients.