Objective: This study compared the prevalence of abnormal results of laboratory tests routinely performed among newly hospitalized psychiatric patients in Spain and the cost-effectiveness of such tests.
Methods: Routine biochemical tests were performed for 510 newly hospitalized psychiatric patients. For all tests, this study examined the prevalence of values outside the normal range and compared the number needed to screen to find one abnormal result (NNSAR=1/prevalence of abnormal results in the studied population) with the direct cost spent to find one abnormal result (DCSAR=NNSAR x direct cost per test).
Results: The prevalence of values outside the normal range ranged from 1% for free thyroxine (FT4) to 36% for total cholesterol. The NNSAR ranged from 2.8 for total cholesterol to 127.3 for FT4. The DCSAR ranged from .38 international dollars of 2000 (I$) for chloride to 402.27 I$ for FT4.
Conclusions: There were large differences in the prevalence of abnormal results (NNSAR) and cost-effectiveness (DCSAR) for the laboratory tests routinely performed among newly admitted psychiatric patients.