Creatine Kinase--MB: The Journey to Obsolescence
Creatine Kinase--MB: The Journey to Obsolescence
When CK-MB was routinely a part of the ACS panel for laboratory tests, the yearly volume was about 12,000 tests, as shown in Figure 1, for 2007 and 2008. The volumes for 2009 and 2010 were lower but did not fully reflect the change, as CK-MB was reintroduced for parts of these years. The test volumes in 2011, 2012, and the first 4 months of 2013 were 113, 90, and 16 patient (billable) tests, respectively. These numbers are patient tests and do not include PT volume. The number of patients tested during these time frames was 92, 68, and 11, respectively. Despite the low volumes in 2011 onward, the laboratory continued to perform daily quality control and related procedures to ensure ready availability of the test Table 1. The total number of tests, including PT, done in 2011, 2012, and the first 4 months of 2013 was 143, 159, and 36, respectively.
(Enlarge Image)
Figure 1.
The creatine kinase (CK)–MB test volume from 2007 through 2013. The numbers for 2013 are extrapolated from the first 4 months. CK-MB was not on the acute coronary syndrome (ACS) panel for portions of 2009 and 2010 and not on the ACS panel in 2011 through 2013.
From January 1, 2011, through April 30, 2013, there were 16 instances in which the CK-MB test was done without any concurrent troponin testing. Thirteen of these 16 tests were ordered by an outreach clinic, ostensibly for the diagnosis of fibromyalgia. One patient was tested following coronary artery bypass grafting (performed at another hospital), and the reason for the CK-MB test could not be ascertained in the other two orders.
The review of medical records of the 171 patients revealed only one patient in whom the CK-MB test provided supporting information. This patient was seen in the emergency department, having been discharged 2 days earlier with a diagnosis of MI (and appropriate treatment). She had chest pain and elevated troponin levels, although the levels were lower than the values noted at discharge. The consultant cardiologist concluded that the troponin levels were consistent with resolving MI and did not comment on the CK-MB values. CK-MB was not elevated and thus could have contributed toward excluding a new MI, although troponin levels were considered sufficient for excluding a new MI or extension of an old MI. CK-MB values did not provide any additional information in the remaining 170 patients.
To ascertain the extent to which laboratories accredited by the CAP may have discontinued CK-MB testing, we examined the number of participants in the CAP PT program for cardiac markers in the 2013 CAR-B challenge. It was our assumption that the laboratories that would have discontinued performing CK-MB testing in-house would no longer be participating in the CK-MB PT program. For the 2013 CAR-B survey, there were 1,995 participants in the troponin I and T PT program and 1,558 participants in the CK-MB PT program. Thus, it would appear that around one-fourth (23%) of the laboratories have discontinued CK-MB testing as part of the cardiac testing menu, although, as discussed later, this figure may be an overestimate.
Results
When CK-MB was routinely a part of the ACS panel for laboratory tests, the yearly volume was about 12,000 tests, as shown in Figure 1, for 2007 and 2008. The volumes for 2009 and 2010 were lower but did not fully reflect the change, as CK-MB was reintroduced for parts of these years. The test volumes in 2011, 2012, and the first 4 months of 2013 were 113, 90, and 16 patient (billable) tests, respectively. These numbers are patient tests and do not include PT volume. The number of patients tested during these time frames was 92, 68, and 11, respectively. Despite the low volumes in 2011 onward, the laboratory continued to perform daily quality control and related procedures to ensure ready availability of the test Table 1. The total number of tests, including PT, done in 2011, 2012, and the first 4 months of 2013 was 143, 159, and 36, respectively.
(Enlarge Image)
Figure 1.
The creatine kinase (CK)–MB test volume from 2007 through 2013. The numbers for 2013 are extrapolated from the first 4 months. CK-MB was not on the acute coronary syndrome (ACS) panel for portions of 2009 and 2010 and not on the ACS panel in 2011 through 2013.
From January 1, 2011, through April 30, 2013, there were 16 instances in which the CK-MB test was done without any concurrent troponin testing. Thirteen of these 16 tests were ordered by an outreach clinic, ostensibly for the diagnosis of fibromyalgia. One patient was tested following coronary artery bypass grafting (performed at another hospital), and the reason for the CK-MB test could not be ascertained in the other two orders.
The review of medical records of the 171 patients revealed only one patient in whom the CK-MB test provided supporting information. This patient was seen in the emergency department, having been discharged 2 days earlier with a diagnosis of MI (and appropriate treatment). She had chest pain and elevated troponin levels, although the levels were lower than the values noted at discharge. The consultant cardiologist concluded that the troponin levels were consistent with resolving MI and did not comment on the CK-MB values. CK-MB was not elevated and thus could have contributed toward excluding a new MI, although troponin levels were considered sufficient for excluding a new MI or extension of an old MI. CK-MB values did not provide any additional information in the remaining 170 patients.
To ascertain the extent to which laboratories accredited by the CAP may have discontinued CK-MB testing, we examined the number of participants in the CAP PT program for cardiac markers in the 2013 CAR-B challenge. It was our assumption that the laboratories that would have discontinued performing CK-MB testing in-house would no longer be participating in the CK-MB PT program. For the 2013 CAR-B survey, there were 1,995 participants in the troponin I and T PT program and 1,558 participants in the CK-MB PT program. Thus, it would appear that around one-fourth (23%) of the laboratories have discontinued CK-MB testing as part of the cardiac testing menu, although, as discussed later, this figure may be an overestimate.
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