We analyzed data from the National Tuberculosis Surveillance System (NTSS) for TB cases reported during 2010 to 2017 and USAPI specimen data collected during October 3, 2015 to September 26, 2018 from a commercial laboratory in Hawaii contracted by the Centers for Disease Control and Prevention (CDC). A TB case is verified by isolation of Mtb complex from a clinical specimen through culture, or a positive nucleic acid amplification test, or by a positive smear; otherwise TB is verified through clinical or provider diagnosis. USAPI includes the 3 US territories of American Samoa (AS), the Commonwealth of the Northern Mariana Islands (CNMI), and Guam (GU) as well as the independent nations of the Federated States of Micronesia (FSM), Republic of the Marshall Islands (RMI), and Republic of Palau (PW).

For each unique patient, a diagnostic specimen was defined as the first or second sputum specimen (i.e., initial diagnostic series) as indicated by the specimen collection date. Transport time was calculated as the median number of days from specimen collection to receipt. Diagnostic specimens were considered optimal quality and quantity if they were of mucoid consistency (determined by visual observation upon receipt) and >5 mL in volume, respectively.⁹ Volume cutoffs were pre-selected by the contracted laboratory.

We computed a Pearson’s chi-square statistic to evaluate associations between quality and quantity of specimens and culture results. An α ≤0.05 was considered significant. CDC determined this public health surveillance activity to be non-research, as defined in 45 CFR 46.102.

During 2010 to 2017, 82,285 TB cases were reported from USAPI (4%), Hawaii (1%), and the rest of the USA (95%) (Table 1). Among all reported cases, the proportion that were culture positive was lower in USAPI (42%) than Hawaii (58%) or the United States (55%). Higher proportions of TB patients in USAPI were verified by clinical or provider diagnosis (54%), compared with less than half of that proportion in Hawaii (24%) and the United States (21%) (Table 1). Among adult patients with pulmonary TB, fewer (57%) had sputum-culture-positivity in USAPI, compared with Hawaii (69%) and the United States (74%). A greater representation of pediatric patients in USAPI contributed, in part, to lower culture positivity in USAPI; adults, who make up 77% of TB cases, were the primary driver of lower sputum-culture positive proportions in USAPI (Supplementary Table 1).

A lower proportion of patients had exclusively extrapulmonary disease in the USAPI (15%) and Hawaii (13%), when compared with the United States (21%). In USAPI, pediatric TB patients represented a higher proportion of all TB patients among those with exclusively pulmonary (21%), exclusively extrapulmonary (28%), or pulmonary with extrapulmonary disease (25%) than corresponding proportions in the United States (≤6% each). (Supplementary Table 1).

The vast majority (97%) of 11,137 specimens evaluated from USAPI were sputa. Two-thirds (66%) were diagnostic specimens (n = 7145) (Supplementary Figure 1, available online).

Overall, 3% of USAPI specimens had both optimal quality and quantity (Table 2). Less than half (40%) of specimens had optimal (mucoid) quality; 7% of specimens had optimal quantity (>5 mL) (Table 2). In FSM (27%) and RMI (47%), less than half of the specimens had optimal quality and a smaller proportion (≤5%) were of optimal quantity. While American Samoa had the highest proportion of sputum specimens with optimal quality (79%), Palau had the highest proportion with optimal quantity (18%) (Supplementary Table 1, available online). The median transport time for receipt at the off-island laboratory was 5.6 days (IQR: 3.2-7.6 days). Only 315 (8%) of the 3,848 watery specimens were culture positive, compared with 504 (18%) of the 2,863 mucoid specimens (Table 2). Among 5,259 specimens with 1 to 5 mL, 721 (14%) were culture positive; 80 (6%) of the 1,357 specimens with <1 mL were culture positive.

Our systematic evaluation of surveillance and laboratory data indicates that 42% of TB patients reported in USAPI had positive sputum-culture positive results during 2010 to 2017. Although a greater proportion of TB cases were pediatric in USAPI (22%) compared to the United States (5%), culture positivity was similar (13% and 11%, respectively). We excluded the effect of HIV status from the analysis due to small numbers (7 HIV positive cases [0.2%] in USAPI). We conclude that pediatric patients and extrapulmonary cases do not account for substantial differences in sputum-culture positivity rates.

We found that 3% of the diagnostic specimens collected during the study period had both optimal quality and quantity. Future evaluations that match diagnostic specimen results to patient surveillance records could provide further insights. Because 3 years may be insufficient to monitor trends, additional long-term monitoring is recommended. Programmatic and laboratory interventions, particularly patient education on sputum collection, and staff training on routine reviews of sputum quality and quantity data, revision of laboratory requisition forms, and monthly reports to monitor trends in transport time and contamination have been implemented. Furthermore, the Australian Respiratory Council has collaborated with the Pacific Island TB Nurses Network to start the “USAPI Sputum Project” with practice guidelines, competency standards, and education resources [Resources-Australian Respiratory Council (thearc.org.au)].

Policies and procedures for optimizing specimen and data collection as well as collaboration and coordination between clinicians, laboratorians, and program staff are essential steps toward improving laboratory results. Routine quality improvement and assurance activities as well as coaching and/or mentorships through virtual communities of practice models¹⁰ might help establish a sputum quality and quantity improvement framework that counters laboratory and programmatic challenges.