EKG results are generally very accurate for detecting a wide range of heart conditions, particularly arrhythmias, ischemia, and previous heart attacks. However, the accuracy of an EKG depends on several factors, including the timing of the test and the nature of the heart problem. For example, intermittent arrhythmias may not be captured if they do not occur during the test, leading to a normal EKG reading even though the patient may have a heart issue. In such cases, doctors may recommend a Holter monitor, which records heart activity over 24 to 48 hours, to capture abnormal rhythms over a longer period.

For detecting ongoing heart attacks, EKGs are highly reliable when used alongside clinical evaluation and other diagnostic tests. However, EKGs may not always detect smaller heart issues or conditions that are not electrical in nature, such as structural problems or mild blockages in the coronary arteries. Therefore, while EKGs are a critical tool in cardiac diagnostics, they are often supplemented by other tests to provide a complete assessment of heart health.

The reliability of COVID-19 Testing largely depends on the type of test used. PCR (Polymerase Chain Reaction) tests are considered the gold standard due to their high sensitivity and accuracy. They can detect even small amounts of the virus's genetic material, making them highly reliable for diagnosing current infections. However, the accuracy of PCR tests can be influenced by factors such as the timing of the test relative to exposure or symptom onset, and the quality of the sample collected.

Rapid antigen tests, while faster and more convenient, are generally less accurate than PCR tests, especially in asymptomatic individuals or those in the early stages of infection. These tests are more likely to yield false negatives, meaning they might miss an active infection. Despite this, rapid tests are still valuable for quickly identifying cases in high-risk settings. Confirmatory PCR testing is often recommended if a rapid test result is negative but there is a strong suspicion of COVID-19.