Table 5.

Recommended initial investigations in returning travellers presenting with undifferentiated fever^a

Investigation	Interpretation
Malaria film ± antigen test (RDT)	•Perform in all patients who have visited a tropical country within 1 year of presentation •The sensitivity of a thick film read by an expert is equivalent to that of an RDT, but blood films are necessary for speciation and parasite count, and should be sent to the reference laboratory for confirmation •Three thick films/RDTs over 72 hours (as an outpatient if appropriate) should be performed to exclude malaria with confidence
FBC	•Lymphopenia: common in viral infection (dengue, HIV) and typhoid •Eosinophilia (>0.45 × 106/litre): can be indicative of infectious cause (e.g. parasitic, fungal) •Thrombocytopenia: malaria, dengue, acute HIV, typhoid, also seen in severe sepsis
U&E, LFTs	•High transaminases consistent with a viral hepatitis, but low-level transaminitis is common in many infections •Isolated high alkaline phosphatase is often found in amoebic lever abscess
Blood cultures	•Two sets should be taken before antibiotics
HIV test	•HIV testing should be offered to all febrile patients
Respiratory virus PCR swab	•Respiratory viral PCR swab should be considered in all patients with fever, coryza ± myalgia. Remember seasonal influenza epidemics occur in the northern and southern hemispheres at different times
EDTA for PCRb	•Early in the illness, PCR tests for specific infections can be performed, e.g. VHF, arboviruses, meningococcal PCR
Serological testsb	•’Geographic panel-based serological tests can be performed at the Rare and Imported Pathogen Laboratory. These are panels of diagnostic tests that group the world into 10 regions based on the global epidemiology of infectious diseases. The specific panel of tests performed will be selected by the laboratory and depend on the symptoms, countries visited and exposures and duration of illness •Amoebic ± hydatid serology should be considered in patients with fever and liver abscess •It can be useful to take a serum sample that can be saved by the laboratory in case additional serological testing is indicated at a later date, e.g. Brucella serology
Urinalysis	•Proteinuria and haematuria in leptospirosis •Haemoglobinuria in malaria (rare)
Chest X-ray ± liver ultrasound

FBC, full blood count; HIV, human immunodeficiency virus; LFTs, liver function tests; PCR, polymerase chain reaction; RDT, rapid diagnostic test; U&E, urea and electrolytes.

^aPatients classified as having a high possibility of VHF following a VHF risk assessment should be discussed with the laboratories. All patients should be tested urgently for malaria. FBC, U&E, LFTs, C-reactive protein, coagulation screen, glucose and blood cultures can be requested for these patients as the risk to laboratory workers from processing samples in routine autoanalysers is low.

^bDiscuss with the National Imported Fever Service to ensure that the correct tests are done. An adequate travel history must be documented on request forms. This includes locations visited, dates of travel, dates of symptom onset and risk activities undertaken. Pathogen-specific request forms are required by the reference laboratory for some infections, such as dengue and other arboviral infections. These are available on the Public Health England (PHE, previously HPA) website.

Source: Adapted from British Infection Society recommendations. See Johnston et al.²