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Over one-third of outpatients prescribed drugs for the first time do not receive recommended laboratory monitoring

Over one-third (39 percent) of outpatients who begin taking drugs that carry a risk of causing organ damage, electrolyte abnormalities, or other problems do not receive recommended laboratory tests before starting the medication, according to a new study. For example, 32 percent of patients dispensed drugs for which a serum creatinine test to determine kidney function is recommended did not have the levels evaluated (range of 12 to 61 percent across drugs); 39 percent did not have liver function testing (range 10 to 75 percent); 32 percent did not have blood monitoring (range 9 to 51 percent); and 34 percent did not have electrolyte monitoring (range 20 to 62 percent).

In other cases, some recommended laboratory tests were done for a medication, while others were not. Thyroid function was evaluated less often than other laboratory tests. For instance, 45 percent of those starting lithium did not have thyroid function evaluated.

Finally, lab testing rates varied widely for different medications. For example, 74 percent of patients started on methotrexate were tested for serum creatinine, a complete blood count, and ALT or AST liver enzymes. Yet, a complete blood count and ALT or AST were monitored in only 46 percent of patients starting carbamezepine.

These variations in testing may be due to several factors, suggest the researchers. Prescribers may be more likely to monitor when a drug is prescribed for prolonged treatment or when they have previously cared for patients who experienced drug toxicity. The findings were based on retrospective analysis of patients in 10 geographically distributed health maintenance organizations, who were newly prescribed 1 of 35 drugs or drug classes with recommended laboratory testing monitoring. The study was supported by the Agency for Healthcare Research and Quality (HS14249).

See "Laboratory monitoring of drugs at initiation of therapy in ambulatory care," by Marsha A. Raebel, Pharm.D., Ella E. Lyons, M.S., Susan E. Andrade, Sc.D., and others, in the December 2005 Journal of General Internal Medicine 20, pp. 1120-1126.

Editor's note: A previous article by the researchers, published in the March 2006 Research Activities (Vol. 307, p. 12) found that computerized alerts and professional collaboration between pharmacists and doctors can improve laboratory monitoring of outpatient drug prescribing.

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