The El Escorial criteria were designed to standardize patient groups for clinical trials but are not as useful in clinical practice; possible ALS as described by the El Escorial criteria is almost always clinically ALS. Differential diagnosis
Because symptoms of ALS can be similar to those of a wide variety of other, more treatable diseases or disorders, appropriate tests must be conducted to exclude the possibility of other conditions. One of these tests is electromyography (EMG), a special recording technique that detects electrical activity in muscles. Certain EMG findings can support the diagnosis of ALS. Another common test measures nerve conduction velocity (NCV). Specific abnormalities in the NCV results may suggest, for example, that the person has a form of peripheral neuropathy (damage to peripheral nerves) or myopathy (muscle disease) rather than ALS. While a magnetic resonance imaging (MRI) is often normal in people with early stage ALS, it can reveal evidence of other problems that may be causing the symptoms, such as a spinal cord tumor, multiple sclerosis, a herniated disc in the neck, syringomyelia, or cervical spondylosis.Based on the persons symptoms and findings from the examination and from these tests, the physician may order tests on blood and urine samples to eliminate the possibility of other diseases, as well as routine laboratory tests.
However, some other regulatory authorities did not agree with the FDA decision, with Japans Pharmaceuticals and Medical Devices Agency stating in 2011 that the "risk-benefit balance of gemtuzumab ozogamicin has not changed from its state at the time of approval".In 2017, Pfizer reapplied for US and EU approval, based on a meta-analysis of prior trials and results of the ALFA-0701 clinical trial, an open-label Phase III trial in 280 older people with AML. In September 2017, gemtuzumab ozogamicin was approved again for use in the United States and in the European Union. See also
Inotuzumab ozogamicin

References
Further reading
AusPAR: Gemtuzumab ozogamicin. Therapeutic Goods Administration (TGA) (Report). October 2020. External links
"Gemtuzumab ozogamicin". Drug Information Portal. U.S. National Library of Medicine. Clinical trial number NCT00372593 for "Combination Chemotherapy With or Without Gemtuzumab in Treating Young Patients With Newly Diagnosed Acute Myeloid Leukemia" at ClinicalTrials.gov