Methods  We performed a retrospective review of a primary care practice's computerized medical record. A computerized search identified all patients with a statin on their medication list and gave their alanine aminotransferase, aspartate aminotransferase, and CK values for 1998. We reviewed the records of all patients for whom these values were significantly or moderately abnormal to determine the values' relationship to statin therapy and outcomes.

Results  During the year of the study, 1014 (85%) of the 1194 patients who had a statin on their medication list had at least 1 monitoring test performed. Of these 1014 patients, 10 (1.0%) had a significant elevation and 5 (0.5%) a moderate elevation of transaminase levels, but none of these abnormalities appeared to be related to statin use. Moreover, 6 (0.9%) patients had at least 1 significantly abnormal CK value but it did not appear to be attributable to a statin; and of the 14 (2.1%) patients who had a moderate CK elevation, it was potentially due to a statin in only 2. There were no documented adverse sequelae associated with these abnormal results.

Conclusions  In this study of statin use in a primary care practice, routine monitoring revealed no cases of significantly or moderately abnormal transaminase values attributable to statins. No significantly abnormal and only 2 moderately abnormal CK values were potentially attributable to statin use. This study questions the usefulness of routine measurement of transaminase and CK levels in all patients taking statins.

In addition to hepatotoxicity, myalgia, myositis, and asymptomatic elevations of serum creatine kinase (CK) have been reported with HMG-CoA reductase inhibitor use. However, clinically significant myopathy—defined in most trials as the association of an elevation of CK levels to more than 10 times the upper limit of the normal range with myalgia or weakness—is infrequent, occurring at a rate equal to that obtained with placebo in most trials.^3-8,15 Despite these data, many physicians routinely screen patients for elevations of CK levels. The risk of myopathy increases in a dose-related fashion and is often attributed to concomitant use of other medications.^16-17 The risk of myopathy also increases with liver or renal dysfunction, age, and serious infections.^18-19 New questions regarding the safety of statins were raised after an increased rate of rhabdomyolysis associated with the use of cerivastatin led to the drug's withdrawal from the market. While all statins have been associated with rare reports of rhabdomyolysis, these reports were apparently more frequent with cerivastatin. It remains unclear if routine screening would have prevented rhabdomyolysis in these patients.

Data regarding adverse events and recommendations concerning routine monitoring of CK and transaminase values come largely from controlled trials. These trials excluded individuals at increased risk for developing myopathy or hepatitis because of other medications or underlying medical conditions.^{1, 3, 6, 20-22} In contrast, the controlled trials on statins may have used higher doses of statin medications than the typical starting doses in a primary care practice. Therefore, these trials may have overestimated the rate of complications.^{3-5,8, 23} In addition, many clinicians discontinue statins well before their patients reach the elevations in transaminase or CK values that were considered clinically significant in these trials. Therefore, these studies may not reflect the rate of adverse effects likely to be found with routine use of these medications in a primary care setting. Furthermore, the yield of screening for abnormalities in transaminase or CK levels among patients taking statins in a primary care setting remains uncertain. If the actual risk of the statin medications is sufficiently low, the cost of screening, the evaluation of minor test result abnormalities, and drug discontinuation could all be avoided. Alternatively, if risks are higher than suggested by prior studies, more frequent and rigorous monitoring may be appropriate.

In this study, we analyzed the laboratory results of patients taking statin medications in an academic primary care practice. We determined the frequency of abnormal results (including both significant and moderate serum transaminase and CK elevations), the response of clinicians to these abnormalities, and patient outcomes.

METHODS

All patients who were taking statins and for whom test results showed significantly or moderately elevated serum levels of transaminase or CK were identified. Significant elevations were defined as more than 3 times the upper limit of the normal range (>120 U/L) for transaminases (alanine aminotransferase [ALT] or aspartate aminotrasferase [AST]) and more than 5 times the upper limit of the normal range (>1000 U/L) for CK. This is consistent with (or more cautious than) prior studies of statin safety.^{6, 8} We defined moderately abnormal transaminase values as 2 to 3 times the upper limit of the normal range (81-120 U/L) and moderately abnormal CK values as 2.5 to 5 times that limit (501-1000 U/L).

A detailed review of the record of every patient with significant or moderate elevations of serum transaminase or CK values was performed to identify whether the abnormalities appeared to be directly attributable to statin use. An abnormal test result was considered attributable to statin use if it could be reasonably explained by no other medical condition or medication use, or if it resolved when the medication was discontinued. For example, if a patient had both an elevated CK serum level and a myocardial infarction, or both an elevated transaminase serum level and symptomatic cholecystitis, and if the abnormalities resolved over time despite continuation of the statin medication, the medication was not considered the cause of abnormal blood test results. In cases when the statin was discontinued because of abnormal laboratory findings, follow-up laboratory results and medical records were reviewed to determine the outcome.

Detailed information was obtained for every patient with significantly or moderately abnormal test results, including dose and type of statin; medical conditions such as liver disease, kidney disease, or the presence of human immunodeficiency virus; alcohol consumption; concurrent medications such as antiretroviral agents, azole antifungals, cyclosporine, fibrates, macrolide antibiotics, and nicotinic acid; symptoms experienced with abnormal laboratory findings; and adverse outcome.^16-17 The computerized medical record used for all patients at this practice includes office notes, discharge summaries, current and past medications, medical problem lists, and laboratory data.

A random sample of the patients taking statins was used to provide demographic data and an estimate of the rate of transaminase and CK monitoring (for patients taking statins for 6 months or longer). We calculated 1-sided confidence intervals based on the exact binomial distribution to provide an upper confidence bound on the probability of statin-related abnormalities.

RESULTS

The number and proportion of patients taking statins who had both transaminase and CK values measured during 1998, though not necessarily because of their statin use; who had a transaminase measurement without CK testing; and who had no testing performed are shown in the tabulation.

At the time of this study, 29% of the patients in the study population were prescribed a statin dosage higher than the recommended starting dosage; moreover, 16% of them had medical conditions or were taking medications associated with an increased risk of myositis or hepatitis in individuals taking statins.

TRANSAMINASE ABNORMALITIES

Of the 1002 patients for whom serum transaminase level was tested, 10 (1.0%) were identified as having a significantly abnormal value; however, these values did not appear to be directly attributable to the statin medication (Table 1).

View this table: [in this window] [in a new window] Table 1. Causes of Significant Serum Transaminase Elevation in Patients Taking Statin Medications

Five additional individuals (0.5%) were identified as having a moderate elevation of serum transaminase. As outlined in Table 2, none of these elevations appeared to be directly related to statin use, and there were no adverse patient outcomes related to these abnormal laboratory findings. The upper bound of the 95% confidence interval for moderately or severely abnormal, statin-related, transaminase serum levels was less than 0.3%.

View this table: [in this window] [in a new window] Table 2. Causes of Moderate Elevation of AST or ALT in Patients Taking Statin Medications

CK ABNORMALITIES

The CK serum concentration of 6 (0.9%) of the 645 patients for whom it was measured (54% of those taking a statin) was identified as severely abnormal (>1000 U/L), but for none of them did it appear to be attributable to statin medication. It was due to a myocardial infarction in 5 patients and related to surgery in the sixth. All values returned to normal at subsequent measurements despite continued statin therapy. The upper bound of the probability for severe statin-related abnormalities in CK serum levels was less than 0.5%, with 95% confidence. Fourteen (2.1%) of the patients monitored had a moderate elevation of serum CK (501-1000 U/L), and it was considered to be potentially due to statin medication in only 2 (0.3%) of them, although neither had new myalgia or weakness. In one of them, testing was prompted by long-standing musculoskeletal complaints that predated statin use and persisted after discontinuation; the patient was noted to have mild and persistent serum elevations of CK (250-500 U/L) even after the statin was discontinued. The second patient's CK elevation was noted in testing performed during an office visit following a traumatic injury requiring sutures, and the CK level quickly returned to normal. In both instances statin therapy was later resumed and CK levels remained normal.

The upper bound of the 95% confidence interval for moderate statin-related CK abnormalities was less than 1.0%.

COMMENT

Prior controlled trials of statin therapy defined clinically significant abnormal laboratory findings as greater than 3 times the upper limit of the normal range for transaminase values and greater than 10 times the upper limit of normal range for CK values with concurrent muscle pain, tenderness, or weakness.^{6, 8} However, many physicians may actually discontinue statin therapy well before values reach these levels of abnormality. We addressed this possibility by reviewing all moderately abnormal transaminase or CK values for patients taking statins. In this population, not even cases of moderately abnormal transaminase values could be attributed to statin medication. We identified 2 patients (representing 0.3% of the monitored patients) with moderately abnormal CK values that might have been attributable to statin use; however, these abnormalities were not associated with symptoms or adverse outcomes. It is unclear even in these cases whether detection of the moderate elevations in CK serum concentrations and discontinuation of statin therapy were beneficial to these patients (by preventing myopathy) or harmful (by discontinuing a beneficial medication).

Already one of the most commonly prescribed classes of medications, statins are likely to be increasingly used given the National Cholesterol Education Program's recent recommendations for an even more aggressive cholesterol management.²⁴ The use of these medications will probably increase even more dramatically if the proposals by pharmaceutical companies to make low-dose statins available without a prescription are accepted by the Food and Drug Administration. Given the prevalence of statin use in a wide range of patients, it is important to identify their actual risk in clinical practice and to establish appropriate monitoring guidelines.

The recent withdrawal of cerivastatin from the market due to reports of an increased rate of rhabdomyolysis raises concerns regarding the safety of this class of medication. While rare cases of rhabdomyolysis have been reported with all statins, the number of events associated with cerivastatin use was significantly higher than for other approved statins. This study further supports the safety of the other drugs in this class, as there were no significant abnormalities in CK serum concentrations attributable to statins. No patients in this study were taking cerivastatin.

Unlike prior randomized controlled trials that evaluated statins for safety and efficacy, our study included individuals at an increased risk for complications due to preexisting medical conditions or concomitant medication use. Despite the broader population evaluated in this study, our data indicate that the incidence of statin-related serum transaminase or CK serum concentration elevations is quite low, even when a more rigorous definition of abnormal laboratory findings is applied.

While careful laboratory monitoring will certainly be needed in individuals at increased risk for hepatitis or myopathy, the data provided by this study question the utility of routine screening in all patients. A reduced need for routine screening would provide a substantial reduction in the overall cost associated with statin use and would prevent the unnecessary evaluation of slightly abnormal laboratory findings as well as the unnecessary discontinuation of a highly effective medication. Statin underutilization is reportedly common^25-29 and perhaps even more prevalent in light of the new National Cholesterol Education Program's recommendations. The costs associated with an increase in appropriate administration of these drugs could be offset, at least in part, by a reduction in monitoring costs and follow-up of abnormalities.

In our practice, approximately 4.1% of 29 000 patients are taking statin medications. Assuming an average cost of $32 and $23 for measurement of ALT and CK, respectively, the semiannual screening of all patients in our practice who take statin medications would cost in excess of $130 000 a year. This cost does not include the additional expense expected from further laboratory testing associated with minor abnormalities discovered during screening; more frequent monitoring, as practiced by many clinicians, would also increase the cost. If, however, only high-risk and symptomatic patients were evaluated, a significant reduction in overall cost and inappropriate drug discontinuation would likely follow, without compromising quality of care.

One of our study's limitations is that 84% of the patients had transaminase values measured, that 54% had CK values measured, and that abnormalities could have occurred in those who did not have routine screening during the year. However, given the awareness of clinicians regarding the reported risks of hepatitis and myopathy among patients taking statins, it is likely that patients with any significant adverse events or outcomes would have been tested and identified. Furthermore, because only 29% of our patients were prescribed a dosage higher than the usual starting dose, a larger sample of patients may be needed to establish more clearly how often important toxic effects related to statin use or dosage occur, and whether any specific monitoring practice could identify and prevent them. Our inclusion of moderately abnormal laboratory findings helps minimize this potential effect of sample size. However, a larger sample size would also help determine if one particular statin has a higher incidence of toxic effects, as has been suggested by recent reports linking cerivastatin with rhabdomyolysis. While prior studies have viewed transaminase values less than 3 times and CK values less than 10 times the upper limit of normal as not clinically relevant, a much longer follow-up would be needed to determine the long-term effect of these abnormalities. Finally, statins could be contributing to these abnormalities in patients with abnormal laboratory findings that persist and are attributed to other causes (such as hepatitis C or alcohol use). The safety of treating such patients with statin medications deserves further investigation.

This study further supports the safety of statin use in a primary care setting and provides evidence that the yield of routine monitoring of serum concentrations of transaminases and CK in all treated patients is quite low. If these results are confirmed by other large series, it is possible that transaminase and CK monitoring could be eliminated altogether in asymptomatic patients without significant risk factors for hepatitis or myopathy.

Accepted for publication June 19, 2002.

We thank Joseph Kannam, MD, Murray Mittleman, MD, Kenneth Mukamal, MD, and Russell Phillips, MD, for their assistance.