Background: Delay in diagnosis of anaemia during preoperative assessment poses logisticproblems, leading to multiple clinic visits, inadequate preoperative management, andunnecessary delay of surgery. Therefore, we tested an instant spectrophotometrichaemoglobin (SpHb) measurement technique to facilitate this assessment. Methods: We evaluated portable instant SpHb vs standard laboratory screening of anaemiabetween March 2012 and December 2013. Paired Hb measurements were performed on726 patients using SpHb (Pronto-7, Masimo Corporation, Irvine, CA, USA) and Hb measuredon the same day using an automated analyser. The results were obtained from a group of638 patients from the pre-anaesthetic clinic with expected normal Hb values, and 88patients from the oncology clinic with known low Hb. Results: Median (range) SpHb was 129.5 (67171) compared with 136 g litre21 (63178) Hbmeasured using the automated system. Identifying Hb below a threshold of 130 g litre21 formales had a high sensitivity (93%), while identifying a threshold of 120 g litre21 for femaleshad lower sensitivity (75%). The specificity for males (77%) and females (81%) was similar.Mean measurement bias and agreement: tolerability interval ratio was 28.1 g litre21 and2.78 for men and 23.1 g litre21 and 2.44 for women. Conclusions: SpHb was sensitive as a preliminary screening tool for detecting true low Hbvalues in males, but less sensitive in females. Instant SpHb measurement may enableprompt routine preoperative anaemia management, but its precision was lower thanexpected.