Marks and associates (2007) examined the potential utility of the investigational PCA3 urine assay to predict the repeat biopsy outcome. Urine was collected after DRE (3 strokes per lobe) from 233 men with serum PSA levels persistently ng/ml or greater and at least one previous negative biopsy. The PCA3 scores were determined using a highly sensitive quantitative assay with TMA. The ability of the PCA3 score to predict the biopsy outcome was assessed and compared with the serum PSA levels. The RNA yield was adequate for analysis in the urine samples from 226 of 233 men (., the informative specimen rate was 97 %). Repeat biopsy revealed prostate cancer in 60 (27 %) of the 226 remaining subjects. Receiver operating characteristic curve analysis yielded an area under the curve of for the PCA3 score. In contrast, the area under the curve for serum PSA was . Using a PCA3 score cutoff of 35, the assay sensitivity was 58 % and specificity 72 %, with an odds ratio of . At PCA3 scores of less than 5, only 12 % of men had prostate cancer on repeat biopsy; at PCA3 scores of greater than 100, the risk of positive biopsy was 50 %. The authors concluded that in men undergoing repeat prostate biopsy to rule out cancer, the urinary PCA3 score was superior to serum PSA determination for predicting the biopsy outcome. The high specificity and informative rate suggest that the PCA3 assay could have an important role in prostate cancer diagnosis.
Heavy consumption of the essential amino acid lysine (as indicated in the treatment of cold sores) has allegedly shown false positives in some and was cited by American shotputter C. J. Hunter as the reason for his positive test, though in 2004 he admitted to a federal grand jury that he had injected nandrolone.  A possible cause of incorrect urine test results is the presence of metabolites from other AAS, though modern urinalysis can usually determine the exact steroid used by analyzing the ratio of the two remaining nandrolone metabolites. As a result of the numerous overturned verdicts, the testing procedure was reviewed by UK Sport . On October 5, 2007, three-time Olympic gold medalist for track and field Marion Jones admitted to use of the drug, and was sentenced to six months in jail for lying to a federal grand jury in 2000. 
Home drug testing kits are a very convenient option for individuals to test and monitor themselves for various drugs/biomarkers at their homes. Although these kits can tell if a drug or a biomarker is present in the sample or not with a reasonable accuracy but they fail to provide precise quantitative measurements on how much exactly is present in there. Laboratory tests, on the other hand, allow precise quantitative measurements and can accurately measure the exact concentration/levels of various test drugs/biomarkers in the test sample. This is crucial because certain markers like CRP are often present in the body fluids even in non-pathological states but only a certain threshold concentration can imply their role in a given pathophysiological state. However, laboratory tests are quite sophisticated and extensive in nature and may cost few extra bucks. Various chromatographic & spectrometric methods are like Atomic absorption furnace, ICP-Mass spectrometry, Electro-thermal atomic absorption spectrometry (ETAAS), Atomic absorption platform, and GC/MS etc. are used in laboratory based testing. For casual periodic monitoring purposes and for drugs/biomarkers where quantitative analysis is not of much significance, rapid drug testing kits are highly useful.