Evaluating the Role of mNGS in Infection Diagnosis

Next-generation Sequencing (NGS) is a modern tool that can analyze many pieces of DNA at once. This technology helps scientists look at the genetic material of various organisms from a single sample. One specific type of NGS, called metagenomic NGS (mNGS), looks at all types of nucleic acids in a sample. This makes it possible to check for many different germs, such as bacteria, viruses, and fungi, without needing to know ahead of time which ones to test for.

Doctors can use mNGS in different situations, such as diagnosing infections in body fluids like cerebrospinal fluid (CSF) and blood (Plasma). This method offers some benefits over traditional testing methods, which often rely on specific tests based on what doctors suspect might be causing an infection. Traditional tests, such as cultures or blood tests, usually need to be ordered based on a doctor’s judgment. In contrast, mNGS can find unexpected germs that may not be considered at first.

However, there are challenges regarding how well mNGS works in diagnosing infections. Some results may indicate harmless germs that do not cause illness. Additionally, DNA from germs can stay in the body even after the infection is gone, which complicates how doctors interpret mNGS results. Research has shown that only a small percentage of mNGS results lead to changes in patient treatment.

Given the importance of using mNGS wisely, healthcare facilities are developing guidelines for when to use this testing. These guidelines help ensure that tests are done only when they are likely to help the patient. Some hospitals have created systems to review requests for mNGS testing, considering the patient's condition and previous test results before approving it.

In a recent study, researchers looked at mNGS testing in patients from two hospital systems that specialize in treating serious conditions, such as cancer and infections. They focused on understanding how well mNGS performs, how it impacts the way doctors manage infections, and how its costs compare to traditional Microbiology tests.

#Study Overview

The approval process for mNGS testing varied between the two hospitals. In one hospital, a committee needed to review and approve requests for mNGS, while the other hospital allowed tests to be ordered without an approval process. This difference led to various practices in testing and differences in how quickly patients received their test results.

The study included patients who received mNGS tests for CSF or plasma. Researchers kept track of the hospital records to see how many tests were done and what results were found. They also tracked whether mNGS results led to any changes in treatment.

#Patient Demographics and Test Results

During the study, 80 patients received mNGS tests, with 28 from one hospital and 52 from the other. Many patients had already received antibiotics before the mNGS tests. In the case of CSF tests, 19% found germs, while plasma tests found germs in 65% of cases. Plasma mNGS tests identified more clinically important germs than the CSF tests did.

Despite the higher detection rate in plasma tests, only a small number of patients had their treatment changed because of the mNGS results. This finding raises questions about how effective mNGS is as a diagnostic tool.

#Impact on Treatment

For patients who received CSF mNGS tests, only one result led to a change in treatment. In contrast, plasma tests had a higher rate, with 31% of results prompting a change in antibiotic management. Notably, in several cases, the changes followed negative results or findings of not clinically significant germs.

#Cost of Testing

A common concern about mNGS is its high cost. The average cost was around $2,000 for plasma tests and $2,900 for CSF tests. The researchers compared these costs with traditional microbiology tests performed on the same patients. They found significant differences in testing volumes and costs between the two hospitals, particularly for CSF mNGS tests.

The hospital that required approval for mNGS testing had more costs associated with traditional microbiology tests before using mNGS. On the other hand, the hospital without the approval process had lower overall testing costs. However, the total expenses related to testing were also influenced by the use of mNGS. About 30-50% of microbiology testing costs came from mNGS tests alone.

#Traditional Microbiology Testing Practices

Traditional microbiology tests were different depending on the type of mNGS test ordered. For CSF tests, the most common tests included cultures of the CSF and blood. Following the mNGS testing, additional tests, such as tissue cultures, were more frequently ordered. In cases of plasma mNGS orders, blood cultures were the most common tests performed.

#Conclusion on Testing Effectiveness

The introduction of mNGS into hospitals offers new possibilities for diagnosing infections. However, its role is still being debated, as the effectiveness of mNGS in clinical practice can vary. In this study, the detection rates for clinically important results were low, with only a small percentage of mNGS results leading to changes in treatment.

The findings suggest that while mNGS can help identify some infectious agents, it may not be necessary in every case, especially when other traditional tests can provide sufficient information. Limiting mNGS to patients with a high likelihood of infection may reduce the turnaround time for results and the chances of identifying non-clinically significant results.

#Recommendations for mNGS Testing

Moving forward, hospitals should create clear guidelines on when to use mNGS testing to ensure it is beneficial for patients. These guidelines can help avoid unnecessary tests and improve the overall efficiency of infection diagnosis. Additionally, hospitals should continue to assess the financial aspects of mNGS to see how it fits within their overall testing budgets.

In summary, mNGS is a promising technology that can offer insights into the presence of infections, yet careful consideration is needed to ensure its appropriate use in clinical settings. Protecting patients from unnecessary testing and focusing on situations where mNGS can genuinely help will be crucial as hospitals adapt to this evolving diagnostic tool.