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. 2020 May;5(5):e002312.
doi: 10.1136/bmjgh-2020-002312.

Diagnostic performance of a point-of-care saliva urea nitrogen dipstick to screen for kidney disease in low-resource settings where serum creatinine is unavailable

Rhys D R Evans  1 , Ulla Hemmila  2 , Henry Mzinganjira  3 , Mwayi Mtekateka  3 , Enos Banda  3 , Naomi Sibale  3 , Zuze Kawale  3 , Chimota Phiri  3 , Gavin Dreyer  2 , Viviane Calice-Silva  4 , Jochen G Raimann  5 , Nathan Levin  6 , Roberto Pecoits-Filho  7 , Ravi Mehta  8 , Etienne Macedo  8
Affiliations

Diagnostic performance of a point-of-care saliva urea nitrogen dipstick to screen for kidney disease in low-resource settings where serum creatinine is unavailable

Rhys D R Evans et al. BMJ Glob Health. 2020 May.

Abstract

Background: Kidney disease is prevalent in low-resource settings worldwide, but tests for its diagnosis are often unavailable. The saliva urea nitrogen (SUN) dipstick is a laboratory and electricity independent tool, which may be used for the detection of kidney disease. We investigated the feasibility and performance of its use in diagnosing kidney disease in community settings in Africa.

Methods: Adult patients at increased risk of kidney disease presenting to three community health centres, a rural district hospital and a central hospital in Malawi were recruited between October 2016 and September 2017. Patients underwent concurrent SUN and creatinine testing at enrolment, and at 1 week, 1 month, 3 months and 6 months thereafter.

Results: Of 710 patients who presented at increased risk of kidney disease, 655 (92.3%) underwent SUN testing at enrolment, and were included (aged 38 (29-52) years, 367 (56%) female and 333 (50.8%) with HIV). Kidney disease was present in 482 (73.6%) patients and 1479 SUN measurements were made overall. Estimated glomerular filtration rate (eGFR) correlated with SUN (r=-0.39; p<0.0001). The area under the receiver operating characteristics curve was 0.61 for presenting SUN to detect acute or chronic kidney disease, and 0.87 to detect severe (eGFR <15 mL/min/1.73 m2) kidney disease (p<0.0001; sensitivity 82.3%, specificity 81.8%, test accuracy 81.8%). In-hospital mortality was greater if enrolment SUN was elevated (>test pad #1) compared with patients with non-elevated SUN (p<0.0001; HR 3.3 (95% CI 1.7 to 6.1).

Conclusions: SUN, measured by dipstick, is feasible and may be used to screen for kidney disease in low resource settings where creatinine tests are unavailable.

Keywords: HIV; health systems; other diagnostic or tool; prevention strategies; screening.

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Conflict of interest statement

Competing interests: None declared.

Figures

Figure 1
Figure 1
Cohort description. SUN, saliva urea nitrogen.
Figure 2
Figure 2
Creatinine and EGFR according to sun result. All SUN tests undertaken at all time points are included. Plots demonstrate median and 95% CIs around the median; statistical significance demonstrated is according to Dunn’s multiple comparison testing (**p<0.01, ***p<0.001, ****p<0.0001). EGFR, estimated glomerular filtration rate; SUN, Saliva Urea Nitrogen.
Figure 3
Figure 3
Receiver operating characteristic curves (ROC) for the performance of SUN (measured by dipstick) to detect any kidney disease (AKI, AKD, or CKD), and presenting eGFRs of <60, 45, 30 and 15 mL/min/1.73 m2. AKI, acute kidney injury; AKD, acute kidney disease; CKD, chronic kidney disease; eGFRs, estimated glomerular filtration rates; SUN, saliva urea nitrogen.
Figure 4
Figure 4
In-hospital survival according to presenting SUN (measured by dipstick). SUN, saliva urea nitrogen.
See this image and copyright information in PMC

References

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