Usefulness and validity of diagnostic nasogastric aspiration in patients without hematemesis

We estimate the test characteristics of nasogastric aspiration to diagnose upper gastrointestinal tract hemorrhage in patients without hematemesis.

In this retrospective cohort study, medical records from patients admitted to 2 urban hospitals between 1997 and 2002 for gastrointestinal tract bleeding without hematemesis were reviewed. Positive nasogastric aspiration results were classified by the severity of hemorrhage, and negative results were classified by the presence or absence of bile. The reference standard for nasogastric aspiration was the source of bleeding-upper versus non--upper gastrointestinal tract--from the hospital discharge summary. Confidence intervals (CIs) for proportions and likelihood ratios (LRs) were calculated.

Of 333 eligible patients, 235 were offered nasogastric aspiration, and 220 accepted the test. Results of 220 attempts were distributed as follows: negative, 158 (72%), including 9 (4%) with bile; nasogastric aspiration aborted, 13 (6%); and positive, 49 (23%), including 4 (2%) that were strongly positive (> or =450 mL red blood). Test characteristics of nasogastric aspiration to detect upper gastrointestinal tract bleeding in 213 patients with a reference standard diagnosis were as follows: sensitivity 42% (95% CI 32% to 51%), specificity 91% (95% CI 83% to 95%), negative predictive value 64% (95% CI 56% to 71%), and positive predictive value 92% (95% CI 79% to 97%). The nasogastric aspiration accurately predicted the source of bleeding in 66% of patients (95% CI 59% to 72%). The likelihood ratio of a positive nasogastric aspiration was 11 (95% CI 4 to 30), and the likelihood ratio of a negative nasogastric aspiration was 0.6 (95% CI 0.5 to 0.7).

In patients without hematemesis, a positive nasogastric aspiration, seen in 23%, indicates probable upper gastrointestinal tract bleeding (LR+ 11), but a negative nasogastric aspiration, seen in 72%, provides little information (LR- 0.6).