Drop In Pneumonia Death Rates Possibly Due To Documentation And Diagnostic Coding Variations

A study in the April 4 issue JAMA reveals, that regardless of data suggesting that pneumonia and inpatient deaths have significantly declined amongst U.S. hospitals, findings indicate that this may be explained due to different trends in documentation and diagnostic coding, instead of improved actual outcomes.

In the United States, pneumonia is a leading cause of illness and mortality among adults and is responsible for over 1 million hospitalizations per year – costing the nation over $10.5 billion.

The researchers explain:

“Given its public health significant, pneumonia has been the target of quality improvement activities for nearly 2 decades.”

According to recent studies, the mortality rate of patients hospitalized with pneumonia has steadily decreased. Although this may be due to improvements in quality or progress in clinical care, the researchers state that it may also represent an artifact of changes in diagnostic coding, whereby the most severe pneumonia cases progressively receive alternative principal diagnoses over time.

Peter K. Lindenauer, M.D., M.Sc., of Baystate Medical Center, Springfield, Mass., and his team set out to examine hospitalization trends and outcomes for individuals with pneumonia, and for patients with respiratory failure, or sepsis in addition to pneumonia.

The team then used different approaches for defining pneumonia in order to compare results. One approach depends on the principal diagnosis of pneumonia, while the other approach also includes individuals with the prime diagnosis of respiratory failure or sepsis in addition to a secondary diagnosis of pneumonia.

The researchers used data from the 2003-2009 releases of the Nationwide Inpatient Sample (NIS), the largest all-payer, publicly available, national hospital database, in order to assess changes in hospitalization and mortality rates among patients with a set of conditions they believed would be not as vulnerable to alterations in coding.

The NIS includes a 20% stratified sample of all short-term, non-federal, non-rehabilitation hospitals. During the study period, the incidence of cases in the NIS data set fluctuated from 7.81 million in 2009 to 8.16 million in 2008.

The researchers found that from 2003 to 2009:

• The rate of patients hospitalized with a main diagnosis of pneumonia declined by 27.4% (5.5 to 4.0 per 1,000).
• The rate of patients hospitalized with a main diagnosis of respiratory failure (with a secondary diagnosis of pneumonia) increased by 9.3% (0.44 to 0.48 per 1,000)
• The rate of patients hospitalized with a main diagnosis of sepsis (with a secondary diagnosis of pneumonia) increased by 177.6% (0.4 to 1.1 per 1,000)
• The annual rate of hospitalization declined by 12.5% (6.3 to 5.6 per 1,000), when the three diagnosis groups were combined to lower the possible effect of alterations in coding practices.

During the same time period, the team found that the rate of inpatient mortality declined for each of the three diagnosis groups. After adjusting for age and sex, the researchers found that among patients with a main diagnosis of pneumonia, inpatient mortality decreased from 5.8% in 2003 to 4.2% in 2009 (relative risk reduction [RRR], 28.2%).

Inpatient mortality declined from 25.1% in 2003 to 22.2% in 2009 (RRR, 12%) among patients with a primary diagnosis of sepsis and a secondary diagnosis of pneumonia, while the rate decreased from 25.1% to 19.2% (RRR, 23.7%) among individuals with a primary diagnosis of respiratory failure.

The authors explained:

“However, within the combined group, the adjusted mortality increased from 8.3 percent in 2003 to 8.8 percent in 2009 (RR increase, 6.0 percent. Further, the combined group demonstrated a small decline in inpatient mortality (8.3 percent to 7.8 percent; RRR, 6.3 percent) instead of the modest increase observed without comorbidity adjustment.”

According to the researchers the annual pneumonia hospitalization rate showed a more modest decrease when the three diagnosis groups were combined. In addition, depending on the approach to risk adjustment the team found there was not much change in the inpatient mortality rate, fluctuating from a small increase to a small decline.

The investigators said:

“These findings have important implications. They suggest that attempts to measure the outcomes of patients with pneumonia by studying only those who receive a principal diagnosis of pneumonia will be biased toward increasingly less severe cases.

This is especially problematic in the context of longitudinal studies that are subject to the effects of temporal trends in coding practice. Furthermore, ongoing efforts to measure and compare the performance of hospitals, such as those currently being carried out by the Centers for Medicare & Medicaid Services, may also be biased if there is variation across hospitals in their use of the sepsis and respiratory failure codes.”

According to the researchers their study “was not designed to identify the cause of changes in the choice of principal diagnosis for patients with pneumonia, increased documentation and coding of sepsis may have been driven by guidelines that defined a broader set of sepsis signs and symptoms, a national campaign focused on the early recognition and treatment of sepsis, and the higher hospital reimbursement rates associated with sepsis and respiratory failure.”

They conclude:

“In conclusion, changing patterns in diagnostic coding provide reason to doubt that improvements in the mortality of patients with a principal diagnosis of pneumonia accurately reflect trends in pneumonia outcomes.

Without taking into account the broader range of principal and secondary diagnosis combinations that can be used to assign codes to a patient with pneumonia, efforts to examine trends in outcomes or to compare hospital performance may produce biased results.”